Compositions and methods for enhancing the immunogenicity of antigens

ABSTRACT

The present invention includes compositions, methods and kits for enhancing the immunogenicity of an antigen via fusion to a Listerial protein. The present invention further encompasses Listeria vaccine strains for enhancing the immunogenicity of an antigen.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending U.S.application Ser. No. 10/239,703, filed Sep. 24, 2002, which is acontinuation-in-part of co-pending U.S. application Ser. No. 09/735,450,filed Dec. 13, 2000, now allowed, which is a continuation-in-part ofco-pending U.S. application Ser. No. 09/537,642, filed Mar. 29, 2000.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was supported in part by funds from the U.S. government(National Cancer Institute Grant No. CA69632) and the U.S. governmentmay therefore have certain rights in the invention.

BACKGROUND OF THE INVENTION

Stimulation of an immune response is dependent upon the presence ofantigens recognized as foreign by the host immune system. Bacterialantigens such as Salmonella enterica and Mycobacterium bovis BCG remainin the phagosome and stimulate CD4 T-cells via antigen presentationthrough major histocompatibility class II molecules. In contrast,bacterial antigens such as Listeria monocytogenes exit the phagosomeinto the cytoplasm. The phagolysosomal escape of L. monocytogenes is aunique mechanism which facilitates major histocompatibility class Iantigen presentation of listerial antigens. This escape is dependentupon the pore-forming sulfhydryl-activated cytolysin, listeriolysin O(LLO).

The ability of L. monocytogenes to break down the vacuole within a hostcell and enter the cytoplasm has led to its use as a recombinantvaccine. U.S. Pat. No. 5,830,702 describes vaccines comprisingattenuated mutants of Listeria spp. genetically engineered to expressforeign antigens in the cytoplasm of infected macrophages and othercells. Several approaches for expressing the antigen in Listeria spp.are described including generation of a fusion protein of a selectedforeign antigen and a listerial protein, preferably an enzyme involvedin lysis of host vacuoles. In particular, a fusion protein encoding thehly promoter and the first 416 amino acids of LLO fused in-frame to theentire coding sequence of the NP antigen was constructed in E.coli andon transformation to Listeria monocytogenes secreted a 105 kDA proteinthat reacts with antiserum to LLO and NP (col. 24 of '702 patent).Recombinant L. monocytogenes secreting a fusion protein comprisinglisteriolysin O and NP (LLO-NP) was demonstrated to target infectedcells for lysis by NP-specific class I-restricted cytotoxic T cells. Incontrast, a hemolysin-negative L. monocytogenes strain expressing LLO-NPpresented the antigen in a class II restricted manner (Ikonimidis etal., J. Exp. Med. 1994 180: 2209-2218). Thus, from these studies it wassurmised that hemolysin-dependent bacterial escape from the vacuole isnecessary for class I presentation in vitro.

The escape function of L. monocytogenes has also been transferred toBacillus subtilis and attenuated Salmonella sp. strains (Bielecki et al.Nature 1990 354: 175-176, Gentschev et al. Infect. Immun. 1995 63:4202-4205). S. enteric and M. bovis BCG vaccine carriers which secretelisteriolysin O have also been constructed (Kaufman, S. H. and Hess, J.Immunol. Lett. January 1999 65: 81-84). These constructs are taught tobe capable of introducing antigens into the MHC class II and MHC class Ipathway, resulting in stimulation of both CD4 and CD8 T-cells.Comparison of S. enterica vaccines which display the same listerialantigen in secreted and somatic form showed the secreted antigen displayto be superior to the somatic antigen display (Kaufman, S. H. and Hess,J. Immunol. Lett. January 1999 65(1-2):81-4).

International Publication No. WO 99/10496 discloses recombinant BCGstrains secreting hemolytically active hly with an improved MHC classI-restricted immune response for use as a vaccine against tuberculosis.

Administration of purified listeriolysin O encapsulated in liposomes hasalso been reported to be effective in the induction of antigen-specificTh1-dependent protective immunity to various kinds of intracellularparasitic bacteria in vivo (Tanabe et al. Infect. Immun. February 199967: 568-75).

PEST sequences in eukaryotic proteins have long been identified. It hasbeen taught that proteins containing amino acid sequences that are richin prolines (P), glutamic acids (E), serines (S) and threonines (T),generally, but not always, flanked by clusters containing severalpositively charged amino acids, have rapid intracellular half-lives(Rogers et al., 1986, Science 234:364-369). Further, it has been shownthat these sequences target the protein to the ubiquitin-proteosomepathway for degradation (Rechsteiner and Rogers TIBS 1996 21:267-271).This pathway is also used by eukaryotic cells to generate immunogenicpeptides that bind to MHC class I and it has been hypothesized that PESTsequences are abundant among eukaryotic proteins that give rise toimmunogenic peptides (Realini et al. FEBS Lett. 1994 348:109-113).Prokaryotic proteins do not normally contain PEST sequences because theydo not have this enzymatic pathway. However, a PEST-like sequence richin the amino acids proline (P), glutamic acid (E), serine (S) andthreonine (T) was recently identified at the amino terminus of LLO anddemonstrated to be essential for L. monocytogenes pathogenicity(Decatur, A. L. and Portnoy, D. A. Science 2000 290:992-995). Decaturand Portnoy teach that the presence of this PEST-like sequence in LLOtargets the protein for destruction by proteolytic machinery of the hostcell so that once the LLO has served its function and facilitated theescape of L. monocytogenes from the phagolysosomal vacuole, it isdestroyed before it can damage the cells.

It has now been found that the immune response to an antigen can beenhanced by fusion of the antigen to a non-hemolytic truncated form oflisteriolysin O (ΔLLO). It is believed that the observed enhanced cellmediated immunity and anti-tumor immunity of the fusion protein resultsfrom the PEST-like sequence present in LLO which targets the antigen forprocessing.

Another Listerial protein, ActA, comprises PEST and PEST-like sequences.ActA is a surface-associated protein, and acts as a scaffold in infectedhost cells to facilitate the polymerization, assembly and activation ofhost actin polymers in order to propel the Listeria organism through thecytoplasm. Shortly after entry into the mammalian cell cytosol, L.monocytogenes induces the polymerization of host actin filaments anduses the force generated by actin polymerization to move, firstintracellularly and then from cell to cell. A single bacterial protein,ActA is responsible for mediating actin nucleation and actin-basedmotility. The ActA protein provides multiple binding sites for hostcytoskeletal components, thereby acting as a scaffold to assemble thecellular actin polymerization machinery. The NH₂ terminus of ActA bindsto monomeric actin and acts as a constitutively active nucleationpromoting factor by stimulating the intrinsic actin nucleation activity.ActA and hly are both members of the 10-kb gene cluster regulated by thetranscriptional activator PrfA, and is upregulated approximately226-fold in the mammalian cytosol.

There exists a long-felt need to develop compositions and methods toenhance the immunogenicity of antigens, especially antigens useful inthe prevention and treatment of tumors and intracellular pathogens. Thepresent invention meets this need.

SUMMARY OF THE INVENTION

The present invention includes a method for enhancing the immunogenicityof an antigen comprising fusing to the antigen a truncated ActA protein,or a fragment thereof.

In one aspect of the present invention, the truncated ActA protein is atleast 95% homologous to the sequence set forth in SEQ ID NO:23.

In another aspect of the present invention, the truncated ActA protein,or fragment thereof, comprises the sequence set forth in SEQ ID NO:23.

In still another aspect of the present invention, the truncated ActAprotein consists of the sequence set forth in SEQ ID NO:23.

The present invention further includes a vector comprising an isolatednucleic acid encoding a truncated ActA protein, or a fragment thereof,and an isolated nucleic acid encoding an antigen, wherein the isolatednucleic acid encoding a truncated ActA protein has 95% identity to thenucleic acid sequence set forth in SEQ ID NO:24, and further whereinwhen the isolated nucleic acid encoding a truncated ActA and theisolated nucleic acid encoding an antigen are expressed in a cell, theisolated nucleic acid encoding a truncated ActA and the isolated nucleicacid encoding an antigen are expressed as a fusion protein.

In one aspect of the present invention, the isolated nucleic acidencoding a truncated ActA protein, or fragment thereof, comprises thesequence set forth in SEQ ID NO:24.

In another aspect of the present invention, the isolated nucleic acidencoding a truncated ActA protein, or fragment thereof, consists of thesequence set forth in SEQ ID NO:24.

The present invention further includes a Listeria vaccine straincomprising an antigen fused to a truncated ActA protein, or fragmentthereof.

In one aspect of the present invention, the truncated ActA protein is atleast 95% homologous to the sequence set forth in SEQ ID NO:23.

In another aspect of the present invention, the truncated ActA protein,or fragment thereof, comprises the sequence set forth in SEQ ID NO:23.

In one aspect of the present invention, the truncated ActA proteinconsists of the sequence set forth in SEQ ID NO:23.

In still another aspect of the present invention, the antigen and thetruncated ActA protein, or fragment thereof, are encoded by a vector.

In another aspect of the present invention, the Listeria vaccine strainis the species Listeria monocytogenes.

The present invention further includes a method of eliciting an enhancedimmune response to an antigen, the method comprising administering to amammal an effective amount of a composition comprising a Listeriavaccine strain, wherein the Listeria vaccine strain comprises an antigenfused to a truncated ActA protein, or a fragment thereof.

In one aspect of the present invention, the mammal is a human.

In still another aspect of the present invention, the truncated ActAprotein is at least 95% homologous to the sequence set forth in SEQ IDNO:23.

In one aspect of the present invention, the truncated ActA protein, orfragment thereof, comprises the sequence set forth in SEQ ID NO:23.

In another aspect of the present invention, the truncated ActA proteinconsists of the sequence set forth in SEQ ID NO:23.

In still another aspect of the present invention, the composition issuspended in a pharmaceutically acceptable carrier.

The present invention further includes a kit for eliciting an enhancedimmune response to an antigen, the kit comprising a Listeria vaccinestrain, wherein the Listeria vaccine strain comprises an antigen fusedto a truncated ActA protein, or fragment thereof, and a pharmaceuticallyacceptable carrier, said kit further comprising an applicator, and aninstructional material for use thereof.

The present invention further includes a kit for eliciting an enhancedimmune response to an antigen, the kit comprising an antigen fused to atruncated ActA protein, or fragment thereof, and a pharmaceuticallyacceptable carrier, said kit further comprising an applicator, and aninstructional material for use thereof.

The present invention further includes an isolated nucleic acid encodinga truncated ActA protein, or a fragment thereof, and an antigen, whereinsaid isolated nucleic acid encoding the truncated ActA protein has 95%identity to the nucleic acid sequence set forth in SEQ ID NO:24.

In one aspect of the present invention, the truncated ActA protein, orfragment thereof, comprises the sequence set forth in SEQ ID NO:24.

In another aspect of the present invention, the truncated ActA proteinconsists of the sequence set forth in SEQ ID NO:24.

The present invention further includes an isolated fusion proteincomprising a truncated ActA protein, or a fragment thereof, and anantigen, wherein said isolated fusion protein comprises a truncated ActAprotein having 95% identity to the amino acid sequence set forth in SEQID NO:23.

In one aspect of the present invention, the truncated ActA protein, orfragment thereof, comprises the sequence set forth in SEQ ID NO:23.

In still another aspect of the present invention, the truncated ActAprotein consists of the sequence set forth in SEQ ID NO:23.

In another aspect of the present invention, the fusion protein issuspended in a pharmaceutically acceptable carrier.

In one aspect of the present invention, the fusion protein is suspendedin a pharmaceutically acceptable carrier.

In another aspect of the present invention, the fusion protein issuspended in a pharmaceutically acceptable carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there are depicted in thedrawings certain embodiments of the invention. However, the invention isnot limited to the precise arrangements and instrumentalities of theembodiments depicted in the drawings.

FIG. 1 is a diagram of an HPV-E7 chromosomal expression systemconstructed by integrating an E7 gene into the Listeria chromosome.

FIG. 2 is a diagram of a preferred multi-copy plasmid containing prfAand E7 fused to a truncated form of the hly gene (Δhly) that producedΔLLO.

FIG. 3 is a graph showing tumor immunotherapeutic efficacy of E7 antigenexpressed in L. monocytogenes. Tumor size in millimeters in mice isshown at 7, 14, 21, 28 and 56 days post tumor-inoculation. Naive miceare depicted by an open-circle; mice administered Lm-LLO-E7 are depictedby a filled circle; mice administered Lm-E7 are depicted by a square;mice administered Lm-Gag are depicted by an open diamond; and miceadministered Lm-LLO-NP are depicted by a filled triangle.

FIG. 4 is a graph showing tumor immunotherapeutic efficacy of NP antigenexpressed in L. monocytogenes. Tumor size in millimeters in mice isshown at 10, 17, 24, and 38 days post tumor-inoculation. Naive mice aredepicted by an X; mice administered Lm-LLO-NP are depicted by a filleddiamond; mice administered Lm-NP are depicted by a square; and miceadministered Lm-Gag are depicted by an open circle.

FIG. 5 is a diagram of various Vaccinia virus constructs expressingdifferent forms of HPV16 E7 protein.

FIG. 6 is a graph showing tumor immunotherapeutic efficacy of antigensexpressed by Vaccinia. Tumor size in millimeters in mice is shown at 7,14, 26, 34, 44, 55 and 65 days post tumor-inoculation. Naive mice aredepicted by a filled triangle; mice administered Vac-LLO-E7 are depictedby an open circle; mice administered Vac-SigE7L are depicted by an X;and mice administered Vac-E7 are depicted by an open diamond.

FIG. 7 depicts a schematic representation of the pActA-E7 expressionsystem used to express and secrete E7 from recombinant Listeriabacteria. The hly promoter (pHLY) drives expression, the prfA gene isused to select retention of the plasmid by recombinant Listeria in vivo.

FIG. 8 depicts a Western blot demonstrating that Lm-ActA-E7 secretes E7.Lane 1 depicts Lm-LLO-E7, lane 2 depicts Lm-ActA-E7.001, lane 3 depictsLm-ActA-E7-2.5.3, lane 4 depicts Lm-ActA-E7-2.5.4.

FIG. 9 is a graph depicting tumor size in mice administered Lm-ActA-E7(rectangles), Lm-E7 (ovals), Lm-LLO-E7 (X), and naive mice(non-vaccinated; solid triangles).

FIG. 10 is a graph depicting the induction of E7 specific IFN-gammasecreting CD8⁺ T cells in the spleens and tumors of mice administeredTC- 1 tumor cells and subsequently administered Lm-E7, Lm-LLO-E7,Lm-ActA-E7 or no vaccine (naive).

FIG. 11 is a graph depicting the induction and penetration of E7specific CD8⁺ cells in the spleens and tumors of mice administered TC-1cells and subsequently administered a recombinant Listeria vaccine(naive, Lm-LLO-E7, Lm-E7, Lm-ActA-E7).

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method for enhancing theimmunogenicity of a selected antigen by fusion of the selected antigento a non-hemolytic truncated form of listeriolysin O. It has now beenfound that fusion of an antigen to a non-hemolytic truncated form oflisteriolysin O results in an antigen with enhanced immunogenicity ascompared to an antigen alone. The truncated form of listeriolysin Ofused to an antigen better enables cell mediated immunity and anti-tumorimmunity as compared to antigen alone. Further, these fusion proteinsneed not be expressed by L. monocytogenes, but rather can be expressedand isolated from other vectors and cell systems routinely used forprotein expression and isolation.

The present invention further comprises a recombinant Listeria vaccinestrain including, inter alia, a fusion protein comprising an ActAprotein, or fragment thereof, fused to an antigen. As demonstrated bythe data disclosed herein, a recombinant Listeria vaccine straincomprising a fusion protein comprising ActA and an antigen, whenadministered to an animal, results in the destruction of existing tumorsand the induction of antigen specific lymphocytes capable ofinfiltrating tumors and other diseases where a cellular immune responseis beneficial. The present invention also encompasses a method foreliciting an enhanced immune response to an antigen by administering acomposition comprising a Listeria vaccine strain comprising, inter alia,an antigen fused to an ActA protein, or fragment thereof. This isbecause, as demonstrated by the data disclosed herein, administeringsuch a composition to an animal results in, among other things, aclearing of tumors, and the superior induction of lymphocytes specificfor tumor antigens when compared to the administration of antigen thatis not fused to an ActA protein, or fragment thereof. Further, thepresent invention comprises a method for enhancing the immunogenicity ofan antigen. That is, as demonstrated by the data disclosed herein,fusing an ActA protein, or fragment thereof, to an antigen, results in,among other things, an improved clearance of tumors in animals and anenhanced antigen-specific immune response.

Definitions

As used herein, each of the following terms has the meaning associatedwith it in this section.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

“ActA protein” is used herein to refer to the Listeria monocytogenessurface protein responsible for actin polymerization in infected cells.A “truncated ActA protein” is used herein to refer to an ActA proteinmissing one or more amino acids from the primary amino acid sequence ofthe native ActA protein. A “truncated ActA protein” comprises 390 aminoacids (SEQ ID NO:23) encoded by 1170 nucleotides (SEQ ID NO:24).

“Antigen” is used herein to refer to a substance that when placed incontact with an organism, results in a detectable immune response. Anantigen may be a lipid, peptide, protein, carbohydrate, nucleic acid, orcombinations and variations thereof.

“Antisense” refers particularly to the nucleic acid sequence of thenon-coding strand of a double stranded DNA molecule encoding a protein,or to a sequence which is substantially homologous to the non-codingstrand. As defined herein, an antisense sequence is complementary to thesequence of a double stranded DNA molecule encoding a protein. It is notnecessary that the antisense sequence be complementary solely to thecoding portion of the coding strand of the DNA molecule. The antisensesequence may be complementary to regulatory sequences specified on thecoding strand of a DNA molecule encoding a protein, which regulatorysequences control expression of the coding sequences.

The terms “complementary” and “antisense” as used herein, are notentirely synonymous. “Antisense” refers particularly to the nucleic acidsequence of the non-coding strand of a double stranded DNA moleculeencoding a protein, or to a sequence which is substantially homologousto the non-coding strand.

By the term “applicator” as the term is used herein, is meant any deviceincluding, but not limited to, a hypodermic syringe, a pipette, and thelike, for administering the proteins and Listeria strains of theinvention to a mammal.

“Complementary” as used herein refers to the broad concept of subunitsequence complementarity between two nucleic acids, e.g., two DNAmolecules. When a nucleotide position in both of the molecules isoccupied by nucleotides normally capable of base pairing with eachother, then the nucleic acids are considered to be complementary to eachother at this position. Thus, two nucleic acids are complementary toeach other when a substantial number (at least 50%) of correspondingpositions in each of the molecules are occupied by nucleotides whichnormally base pair with each other (e.g., A:T and G:C nucleotide pairs).As defined herein, an antisense sequence is complementary to thesequence of a double stranded DNA molecule encoding a protein. It is notnecessary that the antisense sequence be complementary solely to thecoding portion of the coding strand of the DNA molecule. The antisensesequence may be complementary to regulatory sequences specified on thecoding strand of a DNA molecule encoding a protein, which regulatorysequences control expression of the coding sequences.

A “coding region” of a gene consists of the nucleotide residues of thecoding strand of the gene and the nucleotides of the non-coding strandof the gene which are homologous with or complementary to, respectively,the coding region of an mRNA molecule which is produced by transcriptionof the gene.

A “coding region” of an mRNA molecule also consists of the nucleotideresidues of the mRNA molecule which are matched with an anticodon regionof a transfer RNA molecule during translation of the mRNA molecule orwhich encode a stop codon. The coding region may thus include nucleotideresidues corresponding to amino acid residues which are not present inthe mature protein encoded by the mRNA molecule (e.g., amino acidresidues in a protein export signal sequence).

“Encoding” refers to the inherent property of specific sequences ofnucleotides in a polynucleotide, such as a gene, a cDNA, or an mRNA, toserve as templates for synthesis of other polymers and macromolecules inbiological processes having either a defined sequence of nucleotides(i.e., rRNA, tRNA and mRNA) or a defined sequence of amino acids and thebiological properties resulting therefrom. Thus, a gene encodes aprotein if transcription and translation of mRNA corresponding to thatgene produces the protein in a cell or other biological system. Both thecoding strand, the nucleotide sequence of which is identical to the mRNAsequence and is usually provided in sequence listings, and thenon-coding strand, used as the template for transcription of a gene orcDNA, can be referred to as encoding the protein or other product ofthat gene or cDNA.

Unless otherwise specified, a “nucleotide sequence encoding an aminoacid sequence” includes all nucleotide sequences that are degenerateversions of each other and that encode the same amino acid sequence.Nucleotide sequences that encode proteins and RNA may include introns.

“Expression vector” refers to a vector comprising a recombinantpolynucleotide comprising expression control sequences operativelylinked to a nucleotide sequence to be expressed. An expression vectorcomprises sufficient cis-acting elements for expression; other elementsfor expression can be supplied by the host cell or in an in vitroexpression system. Expression vectors include all those known in theart, such as cosmids, plasmids (e.g., naked or contained in liposomes)and viruses (e.g., retroviruses, adenoviruses, and adeno-associatedviruses) that incorporate the recombinant polynucleotide.

A “fusion protein” as used herein refers to a protein wherein theprotein comprises two or more proteins linked together by peptide bondsor other chemical bonds. The proteins can be linked together directly bya peptide or other chemical bond, or with one or more amino acidsbetween the two or more proteins, referred to herein as a spacer.

“Fragment” is used herein to refer to a protein, peptide, or nucleicacid that is shorter or comprises fewer amino acids or nucleotides thanthe full length protein, peptide, or nucleic acid. By way of example, afragment of a protein comprises less than the full length protein.

A “genomic DNA” is a DNA strand which has a nucleotide sequencehomologous with a gene. By way of example, both a fragment of achromosome and a cDNA derived by reverse transcription of a mammalianmRNA are genomic DNAs.

“Homologous” as used herein, refers to the subunit sequence similaritybetween two polymeric molecules, e.g., between two nucleic acidmolecules, e.g., two DNA molecules or two RNA molecules, or between twopolypeptide molecules. When a subunit position in both of the twomolecules is occupied by the same monomeric subunit, e.g., if a positionin each of two DNA molecules is occupied by adenine, then they arehomologous at that position. The homology between two sequences is adirect function of the number of matching or homologous positions, e.g.,if half (e.g., five positions in a polymer ten subunits in length) ofthe positions in two compound sequences are homologous then the twosequences are 50% homologous, if 90% of the positions, e.g., 9 of 10,are matched or homologous, the two sequences share 90% homology. By wayof example, the DNA sequences 3′ATTGCC5′ and 3′TATGGC share 50%homology.

As used herein, “homology” is used synonymously with “identity.”

In addition, when the terms “homology” or “identity” are used herein torefer to the nucleic acids and proteins, it should be construed to beapplied to homology or identity at both the nucleic acid and the aminoacid sequence levels.

As used herein, the terms “gene” and “recombinant gene” refer to nucleicacid molecules comprising an open reading frame encoding a polypeptideof the invention. Such natural allelic variations can typically resultin 1-5% variance in the nucleotide sequence of a given gene. Alternativealleles can be identified by sequencing the gene of interest in a numberof different individuals or organisms. This can be readily carried outby using hybridization probes to identify the same genetic locus in avariety of individuals or organisms. Any and all such nucleotidevariations and resulting amino acid polymorphisms or variations that arethe result of natural allelic variation and that do not alter thefunctional activity are intended to be within the scope of theinvention.

“Immunogenicity” is used herein to refer to the innate ability of anantigen or organism to elicit an immune response in an animal when theantigen or organism is administered to the animal. Thus, “enhancing theimmunogenicity” refers to increasing the ability of an antigen ororganism to elicit an immune response in an animal when the antigen ororganism is administered to an animal. The increased ability of anantigen or organism to elicit an immune response can be measured by,among other things, a greater number of antibodies to an antigen ororganism, a greater diversity of antibodies to an antigen or organism, agreater number of T-cells specific for an antigen or organism, a greatercytotoxic or helper T-cell response to an antigen or organism, and thelike.

As used herein, an “instructional material” includes a publication, arecording, a diagram, or any other medium of expression which can beused to communicate the usefulness of the composition of the inventionfor its designated use. The instructional material of the kit of theinvention may, for example, be affixed to a container which contains thecomposition or be shipped together with a container which contains thecomposition. Alternatively, the instructional material may be shippedseparately from the container with the intention that the instructionalmaterial and the composition be used cooperatively by the recipient.

An “isolated nucleic acid” refers to a nucleic acid segment or fragmentwhich has been separated from sequences which flank it in a naturallyoccurring state, e.g., a DNA fragment which has been removed from thesequences which are normally adjacent to the fragment, e.g., thesequences adjacent to the fragment in a genome in which it naturallyoccurs. The term also applies to nucleic acids which have beensubstantially purified from other components which naturally accompanythe nucleic acid, e.g., RNA or DNA or proteins, which naturallyaccompany it in the cell. The term therefore includes, for example, arecombinant DNA which is incorporated into a vector, into anautonomously replicating plasmid or virus, or into the genomic DNA of aprokaryote or eukaryote, or which exists as a separate molecule (e.g.,as a cDNA or a genomic or cDNA fragment produced by PCR or restrictionenzyme digestion) independent of other sequences. It also includes arecombinant DNA which is part of a hybrid gene encoding additionalpolypeptide sequence.

In the context of the present invention, the following abbreviations forthe commonly occurring nucleic acid bases are used. “A” refers toadenosine, “C” refers to cytidine, “G” refers to guanosine, “T” refersto thymidine, and “U” refers to uridine.

A “Listeria vaccine strain” is used herein to refer to a recombinantListeria organism that expresses a heterologous antigen.

By describing two polynucleotides as “operably linked” is meant that asingle-stranded or double-stranded nucleic acid moiety comprises the twopolynucleotides arranged within the nucleic acid moiety in such a mannerthat at least one of the two polynucleotides is able to exert aphysiological effect by which it is characterized upon the other. By wayof example, a promoter operably linked to the coding region of a gene isable to promote transcription of the coding region.

Preferably, when the nucleic acid encoding the desired protein furthercomprises a promoter/regulatory sequence, the promoter/regulatory ispositioned at the 5′ end of the desired protein coding sequence suchthat it drives expression of the desired protein in a cell. Together,the nucleic acid encoding the desired protein and itspromoter/regulatory sequence comprise a “transgene.”

As used herein, the term “promoter/regulatory sequence” means a nucleicacid sequence which is required for expression of a gene productoperably linked to the promoter/regulatory sequence. In some instances,this sequence may be the core promoter sequence and in other instances,this sequence may also include an enhancer sequence and other regulatoryelements which are required for expression of the gene product. Thepromoter/regulatory sequence may, for example, be one which expressesthe gene product in a tissue specific manner.

A “constitutive” promoter is a nucleotide sequence which, when operablylinked with a polynucleotide which encodes or specifies a gene product,causes the gene product to be produced in a living human cell under mostor all physiological conditions of the cell.

An “inducible” promoter is a nucleotide sequence which, when operablylinked with a polynucleotide which encodes or specifies a gene product,causes the gene product to be produced in a living cell substantiallyonly when an inducer which corresponds to the promoter is present in thecell.

A “tissue-specific” promoter is a nucleotide sequence which, whenoperably linked with a polynucleotide which encodes or specifies a geneproduct, causes the gene product to be produced in a living human cellsubstantially only if the cell is a cell of the tissue typecorresponding to the promoter.

A “polyadenylation sequence” is a polynucleotide sequence which directsthe addition of a poly A tail onto a transcribed messenger RNA sequence.

A “polynucleotide” means a single strand or parallel and anti-parallelstrands of a nucleic acid. Thus, a polynucleotide may be either asingle-stranded or a double-stranded nucleic acid.

The term “nucleic acid” typically refers to large polynucleotides.

The term “oligonucleotide” typically refers to short polynucleotides,generally, no greater than about 50 nucleotides. It will be understoodthat when a nucleotide sequence is represented by a DNA sequence (i.e.,A, T, G, C), this also includes an RNA sequence (i.e., A, U, G, C) inwhich “U” replaces “T.”

Conventional notation is used herein to describe polynucleotidesequences: the left-hand end of a single-stranded polynucleotidesequence is the 5′-end; the left-hand direction of a double-strandedpolynucleotide sequence is referred to as the 5′-direction.

The direction of 5′ to 3′ addition of nucleotides to nascent RNAtranscripts is referred to as the transcription direction. The DNAstrand having the same sequence as an mRNA is referred to as the “codingstrand”; sequences on the DNA strand which are located 5′ to a referencepoint on the DNA are referred to as “upstream sequences”; sequences onthe DNA strand which are 3′ to a reference point on the DNA are referredto as “downstream sequences.”

A “portion” of a polynucleotide means at least at least about twentysequential nucleotide residues of the polynucleotide. It is understoodthat a portion of a polynucleotide may include every nucleotide residueof the polynucleotide.

“Primer” refers to a polynucleotide that is capable of specificallyhybridizing to a designated polynucleotide template and providing apoint of initiation for synthesis of a complementary polynucleotide.Such synthesis occurs when the polynucleotide primer is placed underconditions in which synthesis is induced, i.e., in the presence ofnucleotides, a complementary polynucleotide template, and an agent forpolymerization such as DNA polymerase. A primer is typicallysingle-stranded, but may be double-stranded. Primers are typicallydeoxyribonucleic acids, but a wide variety of synthetic and naturallyoccurring primers are useful for many applications. A primer iscomplementary to the template to which it is designed to hybridize toserve as a site for the initiation of synthesis, but need not reflectthe exact sequence of the template. In such a case, specifichybridization of the primer to the template depends on the stringency ofthe hybridization conditions. Primers can be labeled with, e.g.,chromogenic, radioactive, or fluorescent moieties and used as detectablemoieties.

“Recombinant polynucleotide” refers to a polynucleotide having sequencesthat are not naturally joined together. An amplified or assembledrecombinant polynucleotide may be included in a suitable vector, and thevector can be used to transform a suitable host cell.

A recombinant polynucleotide may serve a non-coding function (e.g.,promoter, origin of replication, ribosome-binding site, etc.) as well.

A “recombinant polypeptide” is one which is produced upon expression ofa recombinant polynucleotide.

“Polypeptide” refers to a polymer composed of amino acid residues,related naturally occurring structural variants, and syntheticnon-naturally occurring analogs thereof linked via peptide bonds,related naturally occurring structural variants, and syntheticnon-naturally occurring analogs thereof. Synthetic polypeptides can besynthesized, for example, using an automated polypeptide synthesizer.

The term “protein” typically refers to large polypeptides.

The term “peptide” typically refers to short polypeptides.

Conventional notation is used herein to portray polypeptide sequences:the left-hand end of a polypeptide sequence is the amino-terminus; theright-hand end of a polypeptide sequence is the carboxyl-terminus.

“Transform”, “transforming”, and “transformation” is used herein torefer to a process of introducing an isolated nucleic acid into theinterior of an organism.

Methods and Compositions

Listeriolysin O (LLO) binds to cholesterol-containing membranes whereinit oligomerizes to form pores. The oligomerization is dependent on thepresence of a reduced cystine residue at position 484 in the sequencethat is required for oligomerization. The hly gene encodes a proproteinof 529 residues (GenBank Accession No. P13128), the first 25 amino acidsare the signal sequence and are cleaved from LLO when it is secreted bythe bacterium. Thus, the full length active LLO protein is approximately504 residues. For purposes of the present invention, by “truncated LLOor ΔLLO” it is meant a fragment of LLO which does not contain theactivation domain at the amino terminus and does not include cystine484.

The present invention also relates to methods and compositions forenhancing cell mediated or anti-tumor immunity of a selected antigen byfusion of the selected antigen to a PEST-like amino acid sequencederived from a prokaryotic organism. For purposes of the presentinvention, by “PEST-like amino acid sequence” it is meant a peptide richin the amino acids proline (P), glutamic acid (E), serine (S) andthreonine (T). In a preferred embodiment the PEST-like amino acidsequence is derived from the amino acid terminus of Listeriolysin O(LLO), a hemolytic virulence factor of L. monocytogenes. In a morepreferred embodiment, the PEST-like amino acid sequence comprisesKENSISSMAPPASPPASPKTPIEKKHADEIDK (SEQ ID NO:1).

Enhanced cell mediated immunity was demonstrated for fusion proteinscomprising an antigen and truncated LLO containing the PEST-like aminoacid sequence, SEQ ID NO: 1. The ΔLLO used in these experiments was 416amino acids long as 88 residues from the amino terminus which isinclusive of the activation domain containing cystine 484 weretruncated. However, it is believed that other ΔLLOs without theactivation domain, and in particular cystine 484, will also beeffective. More particularly, it is believed that fusion of an antigento any ΔLLO including the PEST-like amino acid sequence, SEQ ID NO: 1,can enhance cell mediated and anti-tumor immunity of the antigen.

Enhanced immunogenicity of an antigen following fusion to anon-hemolytic truncated form of listeriolysin O was demonstrated.Specifically, experiments have been performed demonstrating that an L.monocytogenes vector that expresses and secretes a fusion product ofHuman Papilloma Virus (HPV) strain 16 E7 and listeriolysin, whichcomprises the PEST-like amino acid sequence SEQ ID NO:1, is a much morepotent cancer immunotherapeutic for HPV immortalized tumors than astrain of L. monocytogenes that secretes the E7 protein alone.Experiments were also performed demonstrating that a recombinantvaccinia virus that carries the gene for the fusion protein LLO-E7 whichcontains the PEST-like amino acid sequence of SEQ ID NO:1 is a much morepotent cancer immunotherapeutic for HPV immortalized tumors than anisogenic strain of vaccinia that carries the gene for E7 protein alone.In comparison, a short fusion protein Lm-AZ/-E7 comprising the E7antigen fused to the promoter, signal sequence and the first 7 aminoacid residues of LLO was an ineffective anti-tumor immunotherapeutic.This short fusion protein terminates directly before the PEST-likesequence and does not contain it.

The present invention comprises an antigen fused to a truncated ActAprotein, or fragment thereof. This is because, as demonstrated by thedata disclosed herein, an antigen fused to a truncated ActA protein, orfragment thereof, when administered to an animal results in, among otherthings, clearing of existing tumors, and the induction of antigenspecific CD8⁺ cells capable of infiltrating infected or tumor cells.Therefore, as demonstrated by the data disclosed herein, ActA has thefunction or activity of enhancing the immunogenicity of an antigen. Thusthe present invention includes a fusion protein comprising an antigenfused to a truncated ActA protein, or fragment thereof. Fusion proteinscomprising an antigen may be prepared by any suitable method, including,for example, cloning and restriction of appropriate sequences or directchemical synthesis by methods discussed below. Alternatively,subsequences may be cloned and the appropriate subsequences cleavedusing appropriate restriction enzymes. The fragments may then be ligatedto produce the desired DNA sequence. Preferably, DNA encoding theantigen can be produced using DNA amplification methods, for examplepolymerase chain reaction (PCR). First, the segments of the native DNAon either side of the new terminus are amplified separately. The 5′ endof the one amplified sequence encodes the peptide linker, while the 3′end of the other amplified sequence also encodes the peptide linker.Since the 5′ end of the first fragment is complementary to the 3′ end ofthe second fragment, the two fragments (after partial purification, e.g.on LMP agarose) can be used as an overlapping template in a third PCRreaction. The amplified sequence will contain codons, the segment on thecarboxy side of the opening site (now forming the amino sequence), thelinker, and the sequence on the amino side of the opening site (nowforming the carboxyl sequence). The antigen can then be ligated into aplasmid.

The truncated ActA protein, or fragment thereof, and the antigen can beconjugated by any of a number of means well known to those of skill inthe art. Typically the antigen is conjugated, either directly or througha linker (spacer), to the ActA protein. However, where both the antigenand the ActA protein are polypeptides it is preferable to recombinantlyexpress the chimeric molecule as a single-chain fusion protein.

Where the ActA protein and/or the antigen is relatively short (i.e.,less than about 50 amino acids) they may be synthesized using standardchemical peptide synthesis techniques. Where both molecules arerelatively short the chimeric molecule may be synthesized as a singlecontiguous polypeptide. Alternatively the ActA protein and the antigenmay be synthesized separately and then fused by condensation of theamino terminus of one molecule with the carboxyl terminus of the othermolecule thereby forming a peptide bond. Alternatively, the ActA proteinand antigen can each be condensed with one end of a peptide spacermolecule thereby forming a contiguous fusion protein.

The peptides and proteins (i.e. truncated ActA and an antigen) of thepresent invention may be readily prepared by standard, well-establishedsolid-phase peptide synthesis (SPPS) as described by Stewart et al. inSolid Phase Peptide Synthesis, 2nd Edition, 1984, Pierce ChemicalCompany, Rockford, Ill.; and as described by Bodanszky and Bodanszky(The Practice of Peptide Synthesis, 1984, Springer-Verlag, New York). Atthe outset, a suitably protected amino acid residue is attached throughits carboxyl group to a derivatized, insoluble polymeric support, suchas cross-linked polystyrene or polyamide resin. “Suitably protected”refers to the presence of protecting groups on both the alpha-aminogroup of the amino acid, and on any side chain functional groups. Sidechain protecting groups are generally stable to the solvents, reagentsand reaction conditions used throughout the synthesis, and are removableunder conditions which will not affect the final peptide product.Stepwise synthesis of the oligopeptide is carried out by the removal ofthe N-protecting group from the initial amino acid, and couple theretoof the carboxyl end of the next amino acid in the sequence of thedesired peptide. This amino acid is also suitably protected. Thecarboxyl of the incoming amino acid can be activated to react with theN-terminus of the support-bound amino acid by formation into a reactivegroup such as formation into a carbodiimide, a symmetric acid anhydrideor an “active ester” group such as hydroxybenzotriazole orpentafluorophenly esters.

Examples of solid phase peptide synthesis methods include the BOC methodwhich utilized tert-butyloxcarbonyl as the alpha-amino protecting group,and the FMOC method which utilizes 9-fluorenylmethyloxcarbonyl toprotect the alpha-amino of the amino acid residues, both methods ofwhich are well-known by those of skill in the art.

Incorporation of N- and/or C-blocking groups can also be achieved usingprotocols conventional to solid phase peptide synthesis methods. Forincorporation of C-terminal blocking groups, for example, synthesis ofthe desired peptide is typically performed using, as solid phase, asupporting resin that has been chemically modified so that cleavage fromthe resin results in a peptide having the desired C-terminal blockinggroup. To provide peptides in which the C-terminus bears a primary aminoblocking group, for instance, synthesis is performed using ap-methylbenzhydrylamine (MBHA) resin so that, when peptide synthesis iscompleted, treatment with hydrofluoric acid releases the desiredC-terminally amidated peptide. Similarly, incorporation of anN-methylamine blocking group at the C-terminus is achieved usingN-methylaminoethyl-derivatized DVB, resin, which upon HF treatmentreleases a peptide bearing an N-methylamidated C-terminus. Blockage ofthe C-terminus by esterification can also be achieved using conventionalprocedures. This entails use of resin/blocking group combination thatpermits release of side-chain peptide from the resin, to allow forsubsequent reaction with the desired alcohol, to form the esterfunction. FMOC protecting group, in combination with DVB resinderivatized with methoxyalkoxybenzyl alcohol or equivalent linker, canbe used for this purpose, with cleavage from the support being effectedby TFA in dicholoromethane. Esterification of the suitably activatedcarboxyl function e.g. with DCC, can then proceed by addition of thedesired alcohol, followed by deprotection and isolation of theesterified peptide product.

Incorporation of N-terminal blocking groups can be achieved while thesynthesized peptide is still attached to the resin, for instance bytreatment with a suitable anhydride and nitrile. To incorporate anacetyl blocking group at the N-terminus, for instance, the resin coupledpeptide can be treated with 20% acetic anhydride in acetonitrile. TheN-blocked peptide product can then be cleaved from the resin,deprotected and subsequently isolated.

To ensure that the peptide obtained from either chemical or biologicalsynthetic techniques is the desired peptide, analysis of the peptidecomposition should be conducted. Such amino acid composition analysismay be conducted using high resolution mass spectrometry to determinethe molecular weight of the peptide. Alternatively, or additionally, theamino acid content of the peptide can be confirmed by hydrolyzing thepeptide in aqueous acid, and separating, identifying and quantifying thecomponents of the mixture using HPLC, or an amino acid analyzer. Proteinsequencers, which sequentially degrade the peptide and identify theamino acids in order, may also be used to determine definitely thesequence of the peptide.

Prior to its use, the peptide is purified to remove contaminants. Inthis regard, it will be appreciated that the peptide will be purified soas to meet the standards set out by the appropriate regulatory agenciesand guidelines. Any one of a number of a conventional purificationprocedures may be used to attain the required level of purity including,for example, reversed-phase high-pressure liquid chromatography (HPLC)using an alkylated silica column such as C₄-,C₈- or C₁₈-silica. Agradient mobile phase of increasing organic content is generally used toachieve purification, for example, acetonitrile in an aqueous buffer,usually containing a small amount of trifluoroacetic acid. Ion-exchangechromatography can be also used to separate peptides based on theircharge.

Solid phase synthesis in which the C-terminal amino acid of the sequenceis attached to an insoluble support followed by sequential addition ofthe remaining amino acids in the sequence is the preferred method forthe chemical synthesis of the polypeptides of this invention. Techniquesfor solid phase synthesis are described by Barany and Merrifield inSolid-Phase Peptide Synthesis; pp. 3-284 in The Peptides: Analysis,Synthesis, Biology. Vol. 2: Special Methods in Peptide Synthesis, PartA., Merrifield, et al. J. Am. Chem. Soc., 85: 2149-2156 (1963), andStewart et al., Solid Phase Peptide Synthesis, 2nd ed. Pierce Chem. Co.,Rockford, Ill. (1984).

Further, the chimeric fusion proteins of the present invention can besynthesized using recombinant DNA methodology. Generally this involvescreating a DNA sequence that encodes the fusion protein, placing the DNAin an expression cassette, such as the plasmid of the present invention,under the control of a particular promoter/regulatory element, andexpressing the protein.

DNA encoding the fusion protein (e.g. truncated ActA/antigen) of thepresent invention may be prepared by any suitable method, including, forexample, cloning and restriction of appropriate sequences or directchemical synthesis by methods such as the phosphotriester method ofNarang et al. (1979, Meth. Enzymol. 68: 90-99); the phosphodiestermethod of Brown et al. (1979, Meth. Enzymol 68: 109-151); thediethylphosphoramidite method of Beaucage et al. (1981, Tetra. Lett.,22: 1859-1862); and the solid support method of U.S. Pat. No. 4,458,066.

Chemical synthesis produces a single stranded oligonucleotide. This maybe converted into double stranded DNA by hybridization with acomplementary sequence, or by polymerization with a DNA polymerase usingthe single strand as a template. One of skill in the art would recognizethat while chemical synthesis of DNA is limited to sequences of about100 bases, longer sequences may be obtained by the ligation of shortersequences.

Alternatively, subsequences may be cloned and the appropriatesubsequences cleaved using appropriate restriction enzymes. Thefragments may then be ligated to produce the desired DNA sequence.

The present invention includes an isolated nucleic acid encoding atruncated ActA molecule, or a fragment thereof, fused to an antigen,wherein the nucleic acid is at least about 80% homologous, morepreferably at least about 90% homologous with a nucleic acid having thesequence of SEQ ID NO:24. Preferably, the nucleic acid is at least about95% homologous, more preferably at least about 96% homologous with anucleic acid having the sequence of SEQ ID NO:24, more preferably atleast about 97% homologous with a nucleic acid having the sequence ofSEQ ID NO:24, more preferably at least about 98% homologous with anucleic acid having the sequence of SEQ ID NO:24, more preferably atleast about 99% homologous with a nucleic acid having the sequence ofSEQ ID NO:24, most preferably, about 99.9% homologous to SEQ ID NO:24,disclosed herein. Even more preferably, the nucleic acid is SEQ IDNO:24. The isolated nucleic acid of the invention should be construed toinclude an RNA or a DNA sequence encoding an ActA protein of theinvention, and any modified forms thereof, including chemicalmodifications of the DNA or RNA which render the nucleotide sequencemore stable when it is cell free or when it is associated with a cell.Chemical modifications of nucleotides may also be used to enhance theefficiency with which a nucleotide sequence is taken up by a cell or theefficiency with which it is expressed in a cell. Such modifications aredetailed elsewhere herein. Any and all combinations of modifications ofthe nucleotide sequences are contemplated in the present invention.

In other related aspects, the invention includes an isolated nucleicacid encoding a truncated ActA protein and an isolated nucleic acidencoding an antigen operably linked to a nucleic acid comprising apromoter/regulatory sequence such that the nucleic acid is preferablycapable of directing expression of the protein encoded by the nucleicacid. Thus, the invention encompasses expression vectors and methods forthe introduction of exogenous DNA into cells with concomitant expressionof the exogenous DNA in the cells such as those described, for example,in Sambrook et al. (1989, Molecular Cloning: A Laboratory Manual, ColdSpring Harbor Laboratory, New York), and in Ausubel et al. (1997,Current Protocols in Molecular Biology, John Wiley & Sons, New York).

Expression of a truncated ActA protein and an antigen, either alone orfused to a detectable tag polypeptide in a cell or mammal may beaccomplished by generating a plasmid, viral, or other type of vectorcomprising the desired nucleic acid operably linked to apromoter/regulatory sequence which serves to drive expression of theprotein, with or without tag, in cells in which the vector isintroduced. Many promoter/regulatory sequences useful for drivingconstitutive expression of a gene are available in the art and include,but are not limited to, for example, the cytomegalovirus immediate earlypromoter enhancer sequence, the SV40 early promoter, both of which wereused in the experiments disclosed herein, as well as the Rous sarcomavirus promoter, and the like. Moreover, inducible and tissue specificexpression of the nucleic acid encoding a truncated ActA protein and anantigen may be accomplished by placing the nucleic acid encoding atruncated ActA protein and an antigen, with or without a tag, under thecontrol of an inducible or tissue specific promoter/regulatory sequence.Examples of tissue specific or inducible promoter/regulatory sequenceswhich are useful for his purpose include, but are not limited to theMMTV LTR inducible promoter, and the SV40 late enhancer/promoter. Inaddition, promoters which are well known in the art which are induced inresponse to inducing agents such as metals, glucocorticoids, and thelike, are also contemplated in the invention. Thus, it will beappreciated that the invention includes the use of anypromoter/regulatory sequence, which is either known or unknown, andwhich is capable of driving expression of the desired protein operablylinked thereto.

Expressing a truncated ActA protein and an antigen using a vector allowsthe isolation of large amounts of recombinantly produced protein.Selection of any particular plasmid vector or other DNA vector is not alimiting factor in this invention and a wide plethora of vectors arewell-known in the art. Further, it is well within the skill of theartisan to choose particular promoter/regulatory sequences and operablylink those promoter/regulatory sequences to a DNA sequence encoding adesired polypeptide. Such technology is well known in the art and isdescribed, for example, in Sambrook et al. (1989, Molecular Cloning: ALaboratory Manual, Cold Spring Harbor Laboratory, New York), and inAusubel et al. (1997, Current Protocols in Molecular Biology, John Wiley& Sons, New York).

The invention thus includes a vector comprising an isolated nucleic acidencoding a truncated ActA protein and an antigen. The incorporation of adesired nucleic acid into a vector and the choice of vectors iswell-known in the art as described in, for example, Sambrook et al.(1989, Molecular Cloning: A Laboratory Manual, Cold Spring HarborLaboratory, New York), and in Ausubel et al. (1997, Current Protocols inMolecular Biology, John Wiley & Sons, New York).

The invention also includes cells, viruses, proviruses, and the like,containing such vectors. Methods for producing cells comprising vectorsand/or exogenous nucleic acids are well-known in the art. See, forexample, Sambrook et al. (1989, Molecular Cloning: A Laboratory Manual,Cold Spring Harbor Laboratory, New York), and in Ausubel et al. (1997,Current Protocols in Molecular Biology, John Wiley & Sons, New York).

The nucleic acids encoding a truncated ActA protein and an antigen maybe cloned into various plasmid vectors. However, the present inventionshould not be construed to be limited to plasmids or to any particularvector. Instead, the present invention should be construed to encompassa wide plethora of vectors which are readily available and/or well-knownin the art.

The present invention further includes a truncated ActA polypeptide, ora fragment thereof, fused to an antigen, wherein the polypeptide is atleast about 80% homologous, more preferably at least about 90%homologous with a polypeptide sequence having the sequence of SEQ IDNO:23. Preferably, the polypeptide is at least about 95% homologous,more preferably at least about 96% homologous with a polypeptide havingthe sequence of SEQ ID NO:23, more preferably at least about 97%homologous with a polypeptide having the sequence of SEQ ID NO:23, morepreferably at least about 98% homologous with a polypeptide having thesequence of SEQ ID NO:23, more preferably at least about 99% homologouswith a polypeptide having the sequence of SEQ ID NO:23, most preferably,about 99.9% homologous to SEQ ID NO:23, disclosed herein. Even morepreferably, the polypeptide is SEQ ID NO:23.

The present invention should not be construed as being limited solely tothe nucleic and amino acid sequences disclosed herein. Once armed withthe present invention, it is readily apparent to one skilled in the artthat other nucleic acids encoding an ActA protein fused to an antigencan be obtained by following the procedures described herein in theexperimental details section for the generation of other ActA/antigenfusion proteins as disclosed herein (e.g., site-directed mutagenesis,frame shift mutations, and the like), and procedures that are well-knownin the art or to be developed.

Further, any other number of procedures may be used for the generationof derivative or variant forms of an ActA/antigen fusion protein usingrecombinant DNA methodology well known in the art such as, for example,that described in Sambrook et al. (1989, Molecular Cloning: A LaboratoryManual, Cold Spring Harbor Laboratory Press, New York) and Ausubel etal. (1997, Current Protocols in Molecular Biology, Green & Wiley, NewYork), and elsewhere herein.

Procedures for the introduction of amino acid changes in a protein orpolypeptide by altering the DNA sequence encoding the polypeptide arewell known in the art and are also described in Sambrook et al. (1989,supra); Ausubel et al. (1997, supra).

The invention includes a nucleic acid encoding an ActA/antigen fusionprotein wherein a nucleic acid encoding a tag polypeptide is covalentlylinked thereto. That is, the invention encompasses a chimeric nucleicacid wherein the nucleic acid sequence encoding a tag polypeptide iscovalently linked to the nucleic acid encoding an ActA/antigen fusionprotein. Such tag polypeptides are well known in the art and include,for instance, green fluorescent protein (GFP), myc, myc-pyruvate kinase(myc-PK), His₆, maltose biding protein (MBP), an influenza virushemagglutinin tag polypeptide, a flag tag polypeptide (FLAG), and aglutathione-S-transferase (GST) tag polypeptide. However, the inventionshould in no way be construed to be limited to the nucleic acidsencoding the above-listed tag polypeptides. Rather, any nucleic acidsequence encoding a polypeptide which may function in a mannersubstantially similar to these tag polypeptides should be construed tobe included in the present invention.

The nucleic acid comprising a nucleic acid encoding a tag polypeptidecan be used to localize an ActA/antigen fusion protein within a cell, atissue, and/or a whole organism (e.g., a mammalian embryo), detect anActA/antigen fusion protein secreted from a cell, and to study therole(s) of an ActA/antigen fusion protein in a cell. Further, additionof a tag polypeptide facilitates isolation and purification of the“tagged” protein such that the proteins of the invention can be producedand purified readily.

As an example, DNA encoding the fusion protein of the present inventionmay be cloned using DNA amplification methods such as polymerase chainreaction (PCR). Thus, the gene for truncated ActA is PCR amplified,using a sense primer comprising a suitable restriction site and anantisense primer comprising another restriction site, preferably anon-identical restriction site to facilitate cloning. The same isrepeated for the isolated nucleic acid encoding an antigen. Ligation ofthe truncated ActA and antigen sequences and insertion into a plasmid orvector produces a vector encoding truncated ActA joined to a terminus ofthe antigen. The two molecules are joined either directly or by a shortspacer introduced by the restriction site.

While the two molecules are preferably essentially directly joinedtogether, one of skill will appreciate that the molecules may beseparated by a peptide spacer consisting of one or more amino acids.Generally the spacer will have no specific biological activity otherthan to join the proteins or to preserve some minimum distance or otherspatial relationship between them. However, the constituent amino acidsof the spacer may be selected to influence some property of the moleculesuch as the folding, net charge, or hydrophobicity.

The present invention comprises a truncated ActA protein, or fragmentthereof, fused to an antigen. Methods for the fusion of an antigen to anActA protein are disclosed elsewhere herein. The truncated ActA protein,or fragment thereof, of the present invention comprises the ActA aminoacid sequence set forth in SEQ ID NO:23. The skilled artisan willrecognize that the ActA protein of the present invention need not bethat which is set forth exactly in SEQ ID NO:23, but rather that otheralterations, modifications, or changes can be made that retain thefunctional characteristics of an ActA protein fused to an antigen as setforth elsewhere herein.

It will be appreciated, of course, that the peptides may incorporateamino acid residues which are modified without affecting activity. Forexample, the termini may be derivatized to include blocking groups, i.e.chemical substituents suitable to protect and/or stabilize the N- andC-termini from “undesirable degradation”, a term meant to encompass anytype of enzymatic, chemical or biochemical breakdown of the compound atits termini which is likely to affect the function of the compound, i.e.sequential degradation of the compound at a terminal end thereof.

Blocking groups include protecting groups conventionally used in the artof peptide chemistry which will not adversely affect the in vivoactivities of the peptide. For example, suitable N-terminal blockinggroups can be introduced by alkylation or acylation of the N-terminus.Examples of suitable N-terminal blocking groups include C₁-C₅ branchedor unbranched alkyl groups, acyl groups such as formyl and acetylgroups, as well as substituted forms thereof, such as theacetamidomethyl (Acm) group. Desamino analogs of amino acids are alsouseful N-terminal blocking groups, and can either be coupled to theN-terminus of the peptide or used in place of the N-terminal reside.Suitable C-terminal blocking groups, in which the carboxyl group of theC-terminus is either incorporated or not, include esters, ketones oramides. Ester or ketone-forming alkyl groups, particularly lower alkylgroups such as methyl, ethyl and propyl, and amide-forming amino groupssuch as primary amines (—NH₂), and mono- and di-alkyl amino groups suchas methyl amino, ethylamino, dimethylamino, diethylamino,methylethylamino and the like are examples of C-terminal blockinggroups. Descarboxylated amino acid analogues such as agmatine are alsouseful C-terminal blocking groups and can be either coupled to thepeptide's C-terminal residue or used in place of it. Further, it will beappreciated that the free amino and carboxyl groups at the termini canbe removed altogether from the peptide to yield desamino anddescarboxylated forms thereof without affect on peptide activity.

Other modifications can also be incorporated without adversely affectingthe activity and these include, but are not limited to, substitution ofone or more of the amino acids in the natural L-isomeric form with aminoacids in the D-isomeric form. Thus, the peptide may include one or moreD-amino acid resides, or may comprise amino acids which are all in theD-form. Retro-inverso forms of peptides in accordance with the presentinvention are also contemplated, for example, inverted peptides in whichall amino acids are substituted with D-amino acid forms.

Acid addition salts of the present invention are also contemplated asfunctional equivalents. Thus, a peptide in accordance with the presentinvention treated with an inorganic acid such as hydrochloric,hydrobromic, sulfuric, nitric, phosphoric, and the like, or an organicacid such as an acetic, propionic, glycolic, pyruvic, oxalic, malic,malonic, succinic, maleic, fumaric, tataric, citric, benzoic, cinnamie,mandelic, methanesulfonic, ethanesulfonic, p-toluenesulfonic, salicyclicand the like, to provide a water soluble salt of the peptide is suitablefor use in the invention.

The present invention also provides for analogs of truncated ActA, orfragments thereof, proteins or peptides. Analogs can differ fromnaturally occurring proteins or peptides by conservative amino acidsequence differences or by modifications which do not affect sequence,or by both.

For example, conservative amino acid changes may be made, which althoughthey alter the primary sequence of the protein or peptide, do notnormally alter its function. Conservative amino acid substitutionstypically include substitutions within the following groups:

-   -   glycine, alanine;    -   valine, isoleucine, leucine;    -   aspartic acid, glutamic acid;    -   asparagine, glutamine;    -   serine, threonine;    -   lysine, arginine;    -   phenylalanine, tyrosine.

Modifications (which do not normally alter primary sequence) include invivo, or in vitro chemical derivatization of polypeptides, e.g.,acetylation, or carboxylation. Also included are modifications ofglycosylation, e.g., those made by modifying the glycosylation patternsof a polypeptide during its synthesis and processing or in furtherprocessing steps; e.g., by exposing the polypeptide to enzymes whichaffect glycosylation, e.g., mammalian glycosylating or deglycosylatingenzymes. Also embraced are sequences which have phosphorylated aminoacid residues, e.g., phosphotyrosine, phosphoserine, orphosphothreonine.

Also included are polypeptides which have been modified using ordinarymolecular biological techniques so as to improve their resistance toproteolytic degradation or to optimize solubility properties or torender them more suitable as a therapeutic agent. Analogs of suchpolypeptides include those containing residues other than naturallyoccurring L-amino acids, e.g., D-amino acids or non-naturally occurringsynthetic amino acids. The peptides of the invention are not limited toproducts of any of the specific exemplary processes listed herein.

The present invention further comprises an antigen with enhancedimmunogenicity. That is, as the data disclosed herein demonstrate, anantigen fused to a truncated ActA protein, or fragment thereof, whenadministered to an animal, results in a clearance of existing tumors andthe induction of antigen specific cytotoxic lymphocytes capable ofinfiltrating tumor or infected cells. When armed with the presentdisclosure, and the methods and compositions disclosed herein, theskilled artisan will readily realize that the present invention inamenable to treatment and/or prevention of a multitude of diseases.

The antigen fused to the truncated ActA protein, or fragment thereof ispreferably an antigen derived from a tumor or an infectious organism,including, but not limited to fungal pathogens, bacteria, parasites,helminths, viruses, and the like. An antigen comprising the fusionprotein of the present invention includes but is not limited to, tetanustoxoid, hemagglutinin molecules from influenza virus, diphtheria toxoid,HIV gp120, HIV gag protein, IgA protease, insulin peptide B, Spongosporasubterranea antigen, vibriose antigens, Salmonella antigens,pneumococcus antigens, respiratory syncytial virus antigens, Haemophilusinfluenza outer membrane proteins, Helicobacter pylori urease, Neisseriameningitidis pilins, N. gonorrhoeae pilins, the melanoma-associatedantigens (TRP-2, MAGE-1, MAGE-3, gp-100, tyrosinase, MART-1, HSP-70,beta-HCG), human papilloma virus antigens E1, E2, E6 and E7 from typeHPV-16, -18, -31, -33, -35 or -45 human papilloma viruses, the tumorantigens CEA, the ras protein, mutated or otherwise, the p53 protein,mutated or otherwise, Muc1, pSA, the antigens well known in the art fromthe following diseases; cholera, diphtheria, Haemophilus, hepatitis A,hepatitis B, influenza, measles, meningitis, mumps, pertussis, smallpox, pneumococcal pneumonia, polio, rabies, rubella, tetanus,tuberculosis, typhoid, Varicella-zoster, whooping cough, yellow fever,the immunogens and antigens from Addison's disease, allergies,anaphylaxis, Bruton's syndrome, cancer, including solid and blood bornetumors, eczema, Hashimoto's thyroiditis, polymyositis, dermatomyositis,type I diabetes mellitus, acquired immune deficiency syndrome,transplant rejection, such as kidney, heart, pancreas, lung, bone, andliver transplants, Graves' disease, polyendocrine autoimmune disease,hepatitis, microscopic polyarteritis, polyarteritis nodosa, pemphigus,primary biliary cirrhosis, pernicious anemia, coeliac disease,antibody-mediated nephritis, glomerulonephritis, rheumatic diseases,systemic lupus erthematosus, rheumatoid arthritis, seronegativespondylarthritides, rhinitis, sjogren's syndrome, systemic sclerosis,sclerosing cholangitis, Wegener's granulomatosis, dermatitisherpetiformis, psoriasis, vitiligo, multiple sclerosis,encephalomyelitis, Guillain-Barre syndrome, myasthenia gravis,Lambert-Eaton syndrome, sclera, episclera, uveitis, chronicmucocutaneous candidiasis, urticaria, transient hypogammaglobulinemia ofinfancy, myeloma, X-linked hyper IgM syndrome, Wiskott-Aldrich syndrome,ataxia telangiectasia, autoimmune hemolytic anemia, autoimmunethrombocytopenia, autoimmune neutropenia, Waldenstrom'smacroglobulinemia, amyloidosis, chronic lymphocytic leukemia,non-Hodgkin's lymphoma, malarial circumsporozite protein, microbialantigens, viral antigens, autoantigens, and lesteriosis.

Tumor antigens contemplated in the present invention include, but arenot limited to, any of the various MAGEs (Melanoma-Associated AntigenE), including MAGE 1 (e.g., GenBank Accession No. M77481), MAGE 2 (e.g.,GenBank Accession No. U03735), MAGE 3, MAGE 4, etc.; any of the varioustyrosinases; mutant ras; mutant p53 (e.g., GenBank Accession No. X54156and AA494311); and p97 melanoma antigen (e.g., GenBank Accession No.M12154). Other tumor-specific antigens include the Ras peptide and p53peptide associated with advanced cancers, the HPV 16/18 and E6/E7antigens associated with cervical cancers, MUC 1 -KLH antigen associatedwith breast carcinoma (e.g., GenBank Accession No. J0365 1), CEA(carcinoembryonic antigen) associated with colorectal cancer (e.g.,GenBank Accession No. X983 11), gp100 (e.g., GenBank Accession No.S73003) or MART1 antigens associated with melanoma, and the PSA antigenassociated with prostate cancer (e.g., GenBank Accession No. X14810).The p53 gene sequence is known (See e.g., Harris et al. (1986) Mol.Cell. Biol., 6:4650-4656) and is deposited with GenBank under AccessionNo. M14694. Tumor antigens encompassed by the present invention furtherinclude, but are not limited to, Her-2/Neu (e.g. GenBank Accession Nos.M16789.1, M16790.1, M16791.1, M16792.1), NY-ESO-1 (e.g. GenBankAccession No. U87459), hTERT (aka telomerase) (GenBank Accession. Nos.NM003219 (variant 1), NM198255 (variant 2), NM 198253 (variant 3), andNM 198254 (variant 4), proteinase 3 (e.g. GenBank Accession Nos. M29142,M75154, M96839, X55668, NM 00277, M96628 and X56606) HPV E6 and E7 (e.g.GenBank Accession No. NC 001526) and WT-1 (e.g. GenBank Accession Nos.NM000378 (variant A), NM024424 (variant B), NM 024425 (variant C), andNM024426 (variant D)). Thus, the present invention can be used asimmunotherapeutics for cancers including, but not limited to, cervical,breast, colorectal, prostate, lung cancers, and for melanomas.

The present invention further includes, but is not limited to theantigens from the following infectious diseases; measles, mumps,rubella, poliomyelitis, hepatitis A, B (e.g., GenBank Accession No.E02707), and C (e.g., GenBank Accession No. E06890), as well as otherhepatitis viruses, influenza, adenovirus (e.g., types 4 and 7), rabies(e.g., GenBank Accession No. M34678), yellow fever, Japaneseencephalitis (e.g., GenBank Accession No. E07883), dengue (e.g., GenBankAccession No. M24444), hantavirus, and HIV (e.g., GenBank Accession No.U18552). Bacterial and parasitic antigens will be derived from knowncausative agents responsible for diseases including, but not limited to,diphtheria, pertussis (e.g., GenBank Accession No. M35274), tetanus(e.g., GenBank Accession No. M64353), tuberculosis, bacterial and fungalpneumonias (e.g., Haemophilus influenzae, Pneumocystis carinii, etc.),cholera, typhoid, plague, shigellosis, salmonellosis (e.g., GenBankAccession No. L03833), Legionnaire's Disease, Lyme disease (e.g.,GenBank Accession No. U59487), malaria (e.g., GenBank Accession No.X53832), hookworm, onchocerciasis (e.g., GenBank Accession No. M27807),schistosomiasis (e.g., GenBank Accession No. L08198), trypanosomiasis,leshmaniasis, giardiasis (e.g., GenBank Accession No. M33641),amoebiasis, filariasis (e.g., GenBank Accession No. J03266),borreliosis, and trichinosis.

The antigens of these and other diseases are well known in the art, andthe skilled artisan, when equipped with the present disclosure and themethods and techniques described herein will readily be able toconstruct a fusion protein comprising a truncated ActA protein and anantigen for use in the present invention.

The skilled artisan, when armed with the present disclosure and the dataherein, will readily appreciate that a truncated ActA protein, orfragments thereof, can be fused to the antigens enumerated herein, andothers well known in the art. While not wishing to be bound by anyparticular theory, the data disclosed herein demonstrate that an antigenfused to an ActA protein, or fragment thereof, is processed in thecellular cytoplasm and presented in the context of the majorhistocompatability complex to effector lymphocytes. Therefore, as iswell known by those having knowledge of the fundamental tenets ofimmunology, an antigen fused to an ActA protein, or fragment thereof,will be degraded through well-known cellular pathways and be displayedon the cell surface for recognition by effector and helper lymphocytes.As is well known in the art, the degradation process results in shortpeptide sequences presented in the context of the majorhistocompatability complex that are subsequently recognized by T-cells,resulting in effector or helper functions. Thus, the secondary, tertiaryand quaternary structures of the antigen fused to a truncated ActAprotein, or fragment thereof are not necessarily material to the presentinvention. However the primary amino acid sequence of the antigen ismaterial to the methods and compositions presented herein. Asdemonstrated by the data disclosed herein, the antigen is recognized bylymphocytes according to short T cell epitopes, the structure of whichis not modified, altered, or otherwise changed by fuision to anotherprotein. Thus, while the present invention is described in reference tocertain antigens, the skilled artisan will readily appreciate that thepresent invention is amendable to any antigen disclosed herein orotherwise well known in the art.

In a first set of experiments, the HPV-E7 antigen was expressed in L.monocytogenes. An L. monocytogenes recombinant that expressed E7 wasmade by chromosomal integration of the E7 gene under the control of thehly promoter and with the inclusion of the hly signal sequence to ensuresecretion of the gene product. The site of integration into thechromosome by homologous recombination was into a region that isnon-essential for Lm virulence. The scheme for this is depicted inFIG. 1. The expression and secretion of the antigen from the resultingrecombinants, Lm-E7, was verified by Western Blot. In addition,therapeutic effects of Lm-E7 were optimized. For example, it was foundthat the best results were achieved delivering the vaccine orally ascompared to parenterally and in a combined protection and regressionmode that requires priming with Lm-E7 before tumor challenge and thenadministering Lm-E7 therapeutically after tumor challenge. Table Iprovides more details for optimized anti-tumor effects observed in thismodel in three different tumor cell lines, TC-1, C3 and EL-4/E7.Bacteria were delivered orally 14 and 7 days prior to tumor challengeand days 7 and 14 following tumor challenge. Delivery of 10⁶ bacteriaintraperitoneally in a similar protocol provided no long-termprotection. However, better protection was observed when Lm-E7 wasdelivered orally. More specifically, with this regimen approximately 50%of the animals remained tumor free in perpetuity and immunizationseriously retarded tumor growth in all animals. TABLE 1 Treatment withLm-E7 Number of tumor free animals versus total in study (numbersurvived) 10⁵ TC-1 on 10⁶ C3 on 5 × 10⁵ EL-4/E7, Treatment Day 60 Day 42Day 40 10⁸ Lm-E7 3/8 (5) 4/8 (8) 4/8 (6) 10⁸ Lm-Gag (ZY-18) 2/8 (2) 0/8(0) 2/8 (0) Naive 0/8 (0) 0/8 (0) 1/8 (0)

Animals administered TC- I or EL-4/E7 tumor cells that were tumor freewere re-challenged on day 60 with TC-1 or day 40 EL-4/E7, respectively.The two animals in each group that had been immunized with Lm-Gag grewtumors whereas the animals immunized with Lm-E7 remained tumor freeuntil termination of the experiment (day 124 in the case of TC- I andday 54 for EL-4/E7).

Compared to results previously disclosed with Lm-NP and the RENCA, CT-26and B16F10-NP models (Pan et al., 1995, Cancer Res. 55:4776-4779), theLm-E7 was less effective than expected. Accordingly, an Lm-E7 constructwas prepared in accordance with the method taught for preparation of theLm-NP construct of Pan et al. (Pan et al., 1995, Cancer Res. 199555:4776-4779).

Specifically, a second L. monocytogenes vaccine that expresses a E7fusion protein, referred to as Lm-LLO-E7, was prepared by complementinga prfA-deletion mutant with a plasmid containing a copy of the prfA geneand a copy of the E7 gene fused to a form of the hly gene truncated toeliminate the hemolytic activity of the enzyme, ΔLLO (see FIG. 2).Functional LLO is maintained by the organism via the endogenouschromosomal copy of hly. The expression and secretion of the fusionprotein was verified by Western blot.

The ability of the Lm-LLO-E7 and Lm-E7 vaccine to induce anti-tumorimmunity was then compared in a regression model. As shown in Table 2,Lm-LLO-E7 was found to be more effective than Lm-E7. This difference inefficacy is believed to be due to the presence of the PEST-likesequence, SEQ ID NO:1, in Lm-LLO-E7. TABLE 2 Number of mice cured ofTC-1 tumor at conclusion of experiment Mice TC-1 free at Mice alive atMice alive at Treatment Day 45 day 45 day 134 Naive 0/8 0/8 0/8Lm-LLO-E7 4/8 8/8 4/8 Lm-E7 0/8 7/8 0/8

Thus, expression of the foreign gene as a fusion protein with ΔLLOenhances the immunogenicity of the antigen.

Additional experiments were performed to compare the ability of Lm-E7with Lm-LLO-E7 to induce the regression of established sub-cutaneousHPV-16 immortalized tumors from C57B1/6 mice. Results from theseexperiments are depicted in FIG. 3. In these experiments, mice wereimmunized i.p. with 0.1 LD⁵⁰ with one of four constructs, Lm-E7, Lm-Gag(isogenic with Lm-E7 except for the antigen expressed), Lm-LLO-E7 orLm-LLO-NP. Lm-LLO-NP is isogenic with Lm-LLO-E7 but expresses influenzaantigen. A second immunization was performed on day 14. As can be seenin FIG. 3, 6 of 8 mice immunized with Lm-LLO-E7 were cured of theirtumors and remained tumor free. None of the other animals demonstratedany regression of the established tumors. Similar results have beenachieved for Lm-LLO-E7 under different immunization protocols. Further,just one immunization has been demonstrated to cure mice of establishedTC-1 of 5 mm diameter. In order to confirm the generality of the findingthat fusing LLO to an antigen confers enhanced immunity, a version ofLm-NP similar to Lm-E7 was constructed. This recombinant was prepared asdepicted in FIG. 1 except that influenza nucleoprotein replaced E7 asthe antigen. The ability of the new Lm-NP was compared with Lm-LLO-NP(described in U.S. Pat. No. 5,830,702 and prepared as depicted in FIG.2). Results from these experiments are depicted in FIG. 4. In theseexperiments, 32 BALB/c mice were inoculated with 5×10⁵ RENCA-NP tumorcells. RENCA-NP is a renal cell carcinoma retrovirally transduced withinfluenza nucleoprotein NP (described in U.S. Pat. No. 5,830,702). Afterpalpable macroscopic tumors had grown on day 10, eight animals in eachgroup were immunized i.p. with 0.1 LD₅₀ with one of three constructs,Lm-NP, Lm-Gag (isogenic with Lm-NP except for the antigen expressed) andLm-LLO-NP. The animals received a second immunization one week later.Eight animals were left untreated. At the end of the experiment on day40, all the mice in the naive group had large tumors or had died. Onlyone mouse in the group that received Lm-Gag and two mice in the groupthat received Lm-NP were tumor free. This experiment demonstrates thatfusing an antigen to LLO is not restricted to E7 and suggests that theform of the antigen is not important.

Additional experiments were performed to confirm the enhancedtherapeutic efficacy of a fusion protein comprising the E7 antigen and atruncated form of listeriolysin O. In these experiments a vacciniavector that expresses E7 as a fusion protein with a non-hemolytictruncated form of listeriolysin O was constructed. The WR strain ofvaccinia was used as the recipient and the fusion gene was excised fromthe listerial plasmid and inserted into pSC11 under the control of thep75 promoter. This vector was chosen because it is the transfer vectorused for the vaccinia constructs Vac-SigE7Lamp and Vac-E7 and wouldtherefore allow direct comparison with Vac-LLO-E7. In this way all threevaccinia recombinants would be expressed under control of the sameearly/late compound promoter p7.5. In addition SC11 allows the selectionof recombinant viral plaques to TK selection and beta-galactosidasescreening.

FIG. 5 depicts the various vaccinia constructs used in theseexperiments. Vac-SigE7Lamp is a recombinant vaccinia virus thatexpressed the E7 protein fused between lysosomal associated membraneprotein (LAMP-1) signal sequence and sequence from the cytoplasmic tailof LAMP-1 (Lin et al. Proc. Natl. Acad. Sci. USA 1995 92:11671-5; Wu etal. Cancer Res. 1996 56:21-6). It was designed to facilitate thetargeting of the antigen to the MHC class II pathway.

The following modifications were made to allow expression of the geneproduct by vaccinia: (a) the T5XT sequence that prevents earlytranscription by vaccinia was removed from the 5′ portion of the LLO-E7sequence by PCR; and (b) an additional XmaI restriction site wasintroduced by PCR to allow the final insertion of LLO-E7 into SC11.Successful introduction of these changes (without loss of the originalsequence that encodes for LLO-E7) was verified by sequencing. Theresultant pSCl 1-E7 construct was used to transfect the TK-ve cell lineCV1 that had been infected with the wildtype vaccinia strain, WR. Celllysates obtained from this co-infection/transfection step containvaccinia recombinants that were plaque purified 3 times. Expression ofthe LLO-E7 fusion product by plaque purified vaccinia was verified byWestern blot using an antibody directed against the LLO proteinsequence. In addition, the ability of Vac-LLO-E7 to produce CD8⁺ T cellsspecific to LLO and E7 was determined using the LLO (91-99) and E7(49-57) epitopes of Balb/c and C57/BL6 mice, respectively. Results wereconfirmed in a chromium release assay.

Tumor rejection studies were performed with TC-1 following the sameprotocol as described herein. Two experiments were performed withdiffering delays before treatment was started. In one experiment,treatments were initiated when the tumors were about 3 mm in diameter(see FIG. 6). As of day 76, 50% of the Vac-LLO-E7 treated mice are tumorfree and 25% of the Vac-SigE7Lamp mice are tumor free.

In a second experiment, TC-1 tumors were grown to a larger size (5 to 6mm). The LLO-E7 fusion protein based vectors were then compared againsta larger number of vectors. Although some of the vaccine groups showedsignificant temporary regression of TC-1, by day 65 the datademonstrates that Lm-LLO-E7 and Vac-LLO-E7 were the most effectivevaccines with respect to the ability to permanently induce theregression of established TC-1. Only 12% of the Vac-SigE7Lamp treatedmice were tumor free while 37% of the Vac-LLO-E7 and Lm-LLO-E7 mice weretumor free. All other mice were dead.

Thus, expression of the antigen as a fusion protein with a non-hemolytictruncated form of listeriolysin O in host cell systems in listeria andhost cell systems other than listeria results in enhanced immunogenicityof the antigen. While comparative experiments were performed withvaccinia, a multitude of other plasmids and expression systems which canbe used to express these fusion proteins are known. For example,bacterial vectors useful in the present invention include, but are notlimited to Salmonella sp., Shigella sp., BCG, L. monocytogenes and S.gordonii. In addition the fusion proteins can be delivered byrecombinant bacterial vectors modified to escape phagolysosomal fusionand live in the cytoplasm of the cell. Viral vectors useful in thepresent invention include, but are not limited to, Vaccinia, Avipox,Adenovirus, AAV, Vaccinia virus NYVAC, Modified vaccinia strain Ankara(MVA), Semliki Forest virus, Venezuelan equine encephalitis virus,herpes viruses, and retroviruses. Naked DNA vectors can also be used.

As a non-limiting example, a commercially available plasmid can be usedin the present invention. Such plasmids are available from a variety ofsources, for example, Invitrogen (La Jolla, Calif.), Stratagene (LaJolla, Calif.), Clontech (Palo Alto, Calif.), or can be constructedusing methods well known in the art. A commercially available plasmidsuch as pCR2.1 (Invitrogen, La Jolla, Calif.), which is a prokaryoticexpression vector with an prokaryotic origin of replication andpromoter/regulatory elements to facilitate expression in a prokaryoticorganism.

The present invention further comprises transforming such a Listeriastrain with a plasmid comprising, inter alia, an isolated nucleic acidencoding a truncated ActA protein, or fragment thereof, and an antigen.As a non-limiting example, if an L. monocytogenes vaccine straincomprises a deletion in the prfA gene or the actA gene, the plasmid cancomprise a prfA or actA gene in order to complement the mutation,thereby restoring function to the L. monocytogenes vaccine strain. Asdescribed elsewhere herein, methods for transforming bacteria are wellknown in the art, and include calcium-chloride competent cell-basedmethods, electroporation methods, bacteriophage-mediated transduction,chemical, and physical transformation techniques (de Boer et al, 1989,Cell 56:641-649; Miller et al, 1995, FASEB J., 9:190-199; Sambrook etal. 1989, Molecular Cloning: A Laboratory Manual, Cold Spring HarborLaboratory, New York; Ausubel et al., 1997, Current Protocols inMolecular Biology, John Wiley & Sons, New York; Gerhardt et al., eds.,1994, Methods for General and Molecular Bacteriology, American Societyfor Microbiology, Washington, D.C.; Miller, 1992, A Short Course inBacterial Genetics, Cold Spring Harbor Laboratory Press, Cold SpringHarbor, N.Y.).

The plasmid of the present invention comprises a promoter/regulatorysequence operably linked to a gene encoding a fusion protein, antigen,amino acid metabolism gene, or combinations thereof.

Plasmids and other expression vectors useful in the present inventionare described elsewhere herein, and can include such features as apromoter/regulatory sequence, an origin of replication for gram negativeand/or gram positive bacteria, and an isolated nucleic acid encoding afusion protein. Further, the isolated nucleic acid encoding a fusionprotein will have its own promoter suitable for driving expression ofsuch an isolated nucleic acid. Promoters useful for driving expressionin a bacterial system are well known in the art, and includebacteriophage lambda, the bla promoter of the beta-lactamase gene ofpBR322, and the CAT promoter of the chloramphenicol acetyl transferasegene of pBR325. Further examples of prokaryotic promoters include themajor right and left promoters of bacteriophage lambda (P_(L) andP_(R)), the trp, recA, lacZ, lacd, and gal promoters of E. coli, thealpha-amylase (Ulmanen et al, 1985. J. Bacteriol. 162:176-182) and theS28-specific promoters of B. subtilis (Gilman et al, 1984 Gene32:11-20), the promoters of the bacteriophages of Bacillus (Gryczan,1982, In: The Molecular Biology of the Bacilli, Academic Press, Inc.,New York), and Streptomyces promoters (Ward et al, 1986, Mol. Gen.Genet. 203:468-478). Additional prokaryotic promoters contemplated inthe present invention are reviewed in, for example, Glick (1987, J. Ind.Microbiol. 1:277-282); Cenatiempo, (1986, Biochimie, 68:505-516); andGottesman, (1984, Ann. Rev. Genet. 18:415-442). Further examples ofpromoter/regulatory elements contemplated in the present inventioninclude, but are not limited to the Listerial prfA promoter (GenBankAcc. No. Y07639), the Listerial hly promoter (GenBank Acc. No. X15127),and the Listerial p60 promoter (GenBank Acc. No. AY126342), or fragmentsthereof.

Proper expression in a prokaryotic cell also requires the presence of aribosome binding site upstream of the gene-encoding sequence. Suchribosome binding sites are disclosed, for example, by Gold, L., et al(1981, Ann. Rev. Microbiol. 35:365-404).

Accordingly, the present invention provides methods for enhancing theimmunogenicity of an antigen via fusion of the antigen to anon-hemolytic truncated form of listeriolysin O or ΔLLO. In oneembodiment, the antigen is fused to the PEST-like amino acid sequence,SEQ ID NO:1, of LLO. The present invention further provides methods andcompositions for enhancing the immunogenicity of an antigen by fusingthe antigen to a truncated ActA protein, or fragment thereof. This isbecause, as demonstrated by the data disclosed herein, an antigen fusedto an ActA protein, when administered to an animal, results in, amongother things, an immune response that clears existing tumors and resultsin the induction of antigen specific cytotoxic lymphocytes.

The present invention also provides methods for enhancing cell mediatedand anti-tumor immunity and compositions with enhanced immunogenicitywhich comprise a PEST-like amino acid sequence derived from aprokaryotic organism fused to or embedded within an antigen. ThePEST-like sequence can be fused to either the amino terminus or thecarboxy terminus of the antigen. As demonstrated herein, fusion of anantigen to the PEST-like sequence of L. monocytogenes enhanced cellmediated and anti-tumor immunity of the antigen. It is believed thatfusion of an antigen to other PEST-like sequences derived from otherprokaryotic organisms will also enhance immunogenicity of the antigen.PEST-like sequence of other prokaryotic organism can be identifiedroutinely in accordance with methods such as described by, for exampleRechsteiner and Rogers (1996, Trends Biochem. Sci. 21:267-271) for L.monocytogenes. Alternatively, PEST-like amino acid sequences from otherprokaryotic organisms can also be identified based by this method. Otherprokaryotic organisms wherein PEST-like amino acid sequences would beexpected to include, but are not limited to, other Listeria species. Forexample, the L. monocytogenes protein ActA contains four such sequences.These are KTEEQPSEVNTGPR (SEQ ID NO:2), KASVTDTSEGDLDSSMQSADEST PQPLK(SEQ ID NO:3), KNEEVNASDFPPPPTDEELR (SEQ ID NO:4), andRGGIPTSEEFSSLNSGDFTDDENSETTEEEIDR (SEQ ID NO:5). Also Streptolysin Ofrom Streptococcus sp. contain a PEST-LIKE sequence. For example,Streptococcus pyogenes Streptolysin O comprises the PEST-like sequenceKQNTASTETTTTNEQPK (SEQ ID NO:6) at amino acids 35-51 and Streptococcusequisimilis Streptolysin O comprises the PEST-like sequenceKQNTANTETTTTNEQPK (SEQ ID NO:7) at amino acids 38-54. Further, thePEST-like sequence can be embedded within the antigenic protein. Thus,for purposes of the present invention, by “fusion” it is meant that theantigenic protein comprises both the antigen and the PEST-like aminoacid sequence either linked at one end of the antigen or embedded withinthe antigen.

In a preferred embodiment, fusion proteins of the present invention areproduced recombinantly via a plasmid which encodes either a truncatedform of the listeriolysin O comprising the PEST-like amino acid sequenceof L. monocytogenes or a PEST-like amino acid sequence derived fromanother prokaryotic organism and the antigen. However, the antigen mayalso be chemically conjugated to the truncated form of listeriolysin Ocomprising the PEST-like amino acid sequence of L. monocytogenes or aPEST-like amino acid sequence derived from another prokaryotic organism.For purposes of the present invention, by “antigen” it is meant toinclude the native antigen gene or gene product or truncated versions ofthese that include identified T cell epitopes. These fusion proteins canthen be incorporated into vaccines for administration to animals,preferably humans, to invoke an enhanced immune response against theantigen of the fusion protein. In one embodiment, the fusion proteins ofthe present invention are delivered as DNA vaccines, RNA vaccines orreplicating RNA vaccines. As will be obvious to those of skill in theart upon this disclosure, vaccines comprising the fusion proteins of thepresent invention are particularly useful in the prevention andtreatment of infectious and neoplastic diseases.

These vaccines may further comprise adjuvants. Examples of adjuvantsuseful in these vaccines include, but are not limited to, unmethylatedCpG, quill glycosides, CFA, QS21, monophosphoryl lipid A, liposomes, andbacterial mitogens and toxins.

The present invention further comprises administering to an animal,preferably a mammal, even more preferably a human, an effective amountof a composition comprising a Listeria vaccine strain. The constructionof such strains is detailed elsewhere herein. The composition comprises,among other things, a pharmaceutically acceptable carrier. That is, asdetailed herein, the composition includes a Listeria vaccine straincomprising a truncated ActA protein, or fragment thereof, fused to anantigen, and a pharmaceutically acceptable carrier.

Pharmaceutically acceptable carriers that are useful include, but arenot limited to, glycerol, water, saline, ethanol and otherpharmaceutically acceptable salt solutions such as phosphates and saltsof organic acids. Examples of these and other pharmaceuticallyacceptable carriers are described in Remington's Pharmaceutical Sciences(1991, Mack Publication Co., New Jersey), the disclosure of which isincorporated by reference in its entirety herein.

The pharmaceutical compositions may be prepared, packaged, or sold inthe form of a sterile injectable aqueous or oily suspension or solution.This suspension or solution may be formulated according to the knownart, and may comprise, in addition to the active ingredient, additionalingredients such as the dispersing agents, wetting agents, or suspendingagents described herein. Such sterile injectable formulations may beprepared using a non-toxic parenterally-acceptable diluent or solvent,such as water or 1,3-butane diol, for example. Other acceptable diluentsand solvents include, but are not limited to, Ringer's solution,isotonic sodium chloride solution, and fixed oils such as syntheticmono- or di-glycerides.

Pharmaceutical compositions that are useful in the methods of theinvention may be administered, prepared, packaged, and/or sold informulations suitable for oral, rectal, vaginal, parenteral, topical,pulmonary, intranasal, buccal, ophthalmic, or another route ofadministration. Other contemplated formulations include projectednanoparticles, liposomal preparations, resealed erythrocytes containingthe active ingredient, and immunologically-based formulations.

The compositions of the invention may be administered via numerousroutes, including, but not limited to, oral, rectal, vaginal,parenteral, topical, pulmonary, intranasal, buccal, or ophthalmicadministration routes. The route(s) of administration will be readilyapparent to the skilled artisan and will depend upon any number offactors including the type and severity of the disease being treated orprevented, the type and age of the veterinary or human patient beingtreated, and the like.

Pharmaceutical compositions that are useful in the methods of theinvention may be administered systemically in oral solid formulations,ophthalmic, suppository, aerosol, topical or other similar formulations.In addition to the compound such as heparan sulfate, or a biologicalequivalent thereof, such pharmaceutical compositions may containpharmaceutically-acceptable carriers and other ingredients known toenhance and facilitate drug administration. Other possible formulations,such as nanoparticles, liposomes, resealed erythrocytes, andimmunologically based systems may also be used to administer thereceptor protein and/or a nucleic acid encoding the same according tothe methods of the invention.

Compounds which are identified using any of the methods described hereinmay be formulated and administered to a mammal for treatment ofinfectious diseases and cancers, are now described.

The invention encompasses the preparation and use of pharmaceuticalcompositions comprising a compound useful for treatment of a widevariety of disorders such as lymphomas, myelomas, carcinomas, melanomas,gliomas, infectious diseases, autoimmune disorders, and the like.

Such a pharmaceutical composition can consist of the active ingredientalone, in a form suitable for administration to a subject, or thepharmaceutical composition may comprise the active ingredient and one ormore pharmaceutically acceptable carriers, one or more additionalingredients, or some combination of these. The active ingredient may bepresent in the pharmaceutical composition in the form of aphysiologically acceptable ester or salt, such as in combination with aphysiologically acceptable cation or anion, as is well known in the art.

As used herein, the term “pharmaceutically acceptable carrier” means achemical composition with which the active ingredient may be combinedand which, following the combination, can be used to administer theactive ingredient to a subject.

As used herein, the term “physiologically acceptable” ester or saltmeans an ester or salt form of the active ingredient which is compatiblewith any other ingredients of the pharmaceutical composition, which isnot deleterious to the subject to which the composition is to beadministered.

The formulations of the pharmaceutical compositions described herein maybe prepared by any method known or hereafter developed in the art ofpharmacology. In general, such preparatory methods include the step ofbringing the active ingredient into association with a carrier or one ormore other accessory ingredients, and then, if necessary or desirable,shaping or packaging the product into a desired single- or multi-doseunit.

Although the descriptions of pharmaceutical compositions provided hereinare principally directed to pharmaceutical compositions that aresuitable for ethical administration to humans, it will be understood bythe skilled artisan that such compositions are generally suitable foradministration to animals of all sorts. Modification of pharmaceuticalcompositions suitable for administration to humans in order to renderthe compositions suitable for administration to various animals is wellunderstood, and the ordinarily skilled veterinary pharmacologist candesign and perform such modification with merely ordinary, if any,experimentation. Subjects to which administration of the pharmaceuticalcompositions of the invention is contemplated include, but are notlimited to, humans and other primates, mammals including commerciallyrelevant mammals such as cattle, pigs, horses, sheep, cats, and dogs.

Pharmaceutical compositions that are useful in the methods of theinvention may be prepared, packaged, or sold in formulations suitablefor oral, rectal, vaginal, parenteral, topical, pulmonary, intranasal,buccal, ophthalmic, intrathecal or another route of administration.Other contemplated formulations include projected nanoparticles,liposomal preparations, resealed erythrocytes containing the activeingredient, and immunologically-based formulations.

A pharmaceutical composition of the invention may be prepared, packaged,or sold in bulk, as a single unit dose, or as a plurality of single unitdoses. As used herein, a “unit dose” is discrete amount of thepharmaceutical composition comprising a predetermined amount of theactive ingredient. The amount of the active ingredient is generallyequal to the dosage of the active ingredient which would be administeredto a subject or a convenient fraction of such a dosage such as, forexample, one-half or one-third of such a dosage.

The relative amounts of the active ingredient, the pharmaceuticallyacceptable carrier, and any additional ingredients in a pharmaceuticalcomposition of the invention will vary, depending upon the identity,size, and condition of the subject treated and further depending uponthe route by which the composition is to be administered. By way ofexample, the composition may comprise between 0. 1% and 100% (w/w)active ingredient.

In addition to the active ingredient, a pharmaceutical composition ofthe invention may further comprise one or more additionalpharmaceutically active agents. Particularly contemplated additionalagents include anti-emetics and scavengers such as cyanide and cyanatescavengers.

Controlled- or sustained-release formulations of a pharmaceuticalcomposition of the invention may be made using conventional technology.

A formulation of a pharmaceutical composition of the invention suitablefor oral administration may be prepared, packaged, or sold in the formof a discrete solid dose unit including, but not limited to, a tablet, ahard or soft capsule, a cachet, a troche, or a lozenge, each containinga predetermined amount of the active ingredient. Other formulationssuitable for oral administration include, but are not limited to, apowdered or granular formulation, an aqueous or oily suspension, anaqueous or oily solution, or an emulsion.

As used herein, an “oily” liquid is one which comprises acarbon-containing liquid molecule and which exhibits a less polarcharacter than water.

A tablet comprising the active ingredient may, for example, be made bycompressing or molding the active ingredient, optionally with one ormore additional ingredients. Compressed tablets may be prepared bycompressing, in a suitable device, the active ingredient in afree-flowing form such as a powder or granular preparation, optionallymixed with one or more of a binder, a lubricant, an excipient, a surfaceactive agent, and a dispersing agent. Molded tablets may be made bymolding, in a suitable device, a mixture of the active ingredient, apharmaceutically acceptable carrier, and at least sufficient liquid tomoisten the mixture. Pharmaceutically acceptable excipients used in themanufacture of tablets include, but are not limited to, inert diluents,granulating and disintegrating agents, binding agents, and lubricatingagents. Known dispersing agents include, but are not limited to, potatostarch and sodium starch glycollate. Known surface active agentsinclude, but are not limited to, sodium lauryl sulphate. Known diluentsinclude, but are not limited to, calcium carbonate, sodium carbonate,lactose, microcrystalline cellulose, calcium phosphate, calcium hydrogenphosphate, and sodium phosphate. Known granulating and disintegratingagents include, but are not limited to, corn starch and alginic acid.Known binding agents include, but are not limited to, gelatin, acacia,pre-gelatinized maize starch, polyvinylpyrrolidone, and hydroxypropylmethylcellulose. Known lubricating agents include, but are not limitedto, magnesium stearate, stearic acid, silica, and talc.

Tablets may be non-coated or they may be coated using known methods toachieve delayed disintegration in the gastrointestinal tract of asubject, thereby providing sustained release and absorption of theactive ingredient. By way of example, a material such as glycerylmonostearate or glyceryl distearate may be used to coat tablets. Furtherby way of example, tablets may be coated using methods described in U.S.Pat. Nos. 4,256,108; 4,160,452; and 4,265,874 to formosmotically-controlled release tablets. Tablets may further comprise asweetening agent, a flavoring agent, a coloring agent, a preservative,or some combination of these in order to provide pharmaceuticallyelegant and palatable preparation.

Hard capsules comprising the active ingredient may be made using aphysiologically degradable composition, such as gelatin. Such hardcapsules comprise the active ingredient, and may further compriseadditional ingredients including, for example, an inert solid diluentsuch as calcium carbonate, calcium phosphate, or kaolin.

Soft gelatin capsules comprising the active ingredient may be made usinga physiologically degradable composition, such as gelatin. Such softcapsules comprise the active ingredient, which may be mixed with wateror an oil medium such as peanut oil, liquid paraffin, or olive oil.

Liquid formulations of a pharmaceutical composition of the inventionwhich are suitable for oral administration may be prepared, packaged,and sold either in liquid form or in the form of a dry product intendedfor reconstitution with water or another suitable vehicle prior to use.

Liquid suspensions may be prepared using conventional methods to achievesuspension of the active ingredient in an aqueous or oily vehicle.Aqueous vehicles include, for example, water and isotonic saline. Oilyvehicles include, for example, almond oil, oily esters, ethyl alcohol,vegetable oils such as arachis, olive, sesame, or coconut oil,fractionated vegetable oils, and mineral oils such as liquid paraffin.Liquid suspensions may further comprise one or more additionalingredients including, but not limited to, suspending agents, dispersingor wetting agents, emulsifying agents, demulcents, preservatives,buffers, salts, flavorings, coloring agents, and sweetening agents. Oilysuspensions may further comprise a thickening agent. Known suspendingagents include, but are not limited to, sorbitol syrup, hydrogenatededible fats, sodium alginate, polyvinylpyrrolidone, gum tragacanth, gumacacia, and cellulose derivatives such as sodium carboxymethylcellulose,methylcellulose, hydroxypropylmethylcellulose. Known dispersing orwetting agents include, but are not limited to, naturally-occurringphosphatides such as lecithin, condensation products of an alkyleneoxide with a fatty acid, with a long chain aliphatic alcohol, with apartial ester derived from a fatty acid and a hexitol, or with a partialester derived from a fatty acid and a hexitol anhydride (e.g.,polyoxyethylene stearate, heptadecaethyleneoxycetanol, polyoxyethylenesorbitol monooleate, and polyoxyethylene sorbitan monooleate,respectively). Known emulsifying agents include, but are not limited to,lecithin and acacia. Known preservatives include, but are not limitedto, methyl, ethyl, or n-propyl-para-hydroxybenzoates, ascorbic acid, andsorbic acid. Known sweetening agents include, for example, glycerol,propylene glycol, sorbitol, sucrose, and saccharin. Known thickeningagents for oily suspensions include, for example, beeswax, hardparaffin, and cetyl alcohol.

Liquid solutions of the active ingredient in aqueous or oily solventsmay be prepared in substantially the same manner as liquid suspensions,the primary difference being that the active ingredient is dissolved,rather than suspended in the solvent. Liquid solutions of thepharmaceutical composition of the invention may comprise each of thecomponents described with regard to liquid suspensions, it beingunderstood that suspending agents will not necessarily aid dissolutionof the active ingredient in the solvent. Aqueous solvents include, forexample, water and isotonic saline. Oily solvents include, for example,almond oil, oily esters, ethyl alcohol, vegetable oils such as arachis,olive, sesame, or coconut oil, fractionated vegetable oils, and mineraloils such as liquid paraffin.

A pharmaceutical composition of the invention may also be prepared,packaged, or sold in the form of oil-in-water emulsion or a water-in-oilemulsion. The oily phase may be a vegetable oil such as olive or arachisoil, a mineral oil such as liquid paraffin, or a combination of these.Such compositions may further comprise one or more emulsifying agentssuch as naturally occurring gums such as gum acacia or gum tragacanth,naturally-occurring phosphatides such as soybean or lecithinphosphatide, esters or partial esters derived from combinations of fattyacids and hexitol anhydrides such as sorbitan monooleate, andcondensation products of such partial esters with ethylene oxide such aspolyoxyethylene sorbitan monooleate. These emulsions may also containadditional ingredients including, for example, sweetening or flavoringagents.

As used herein, “parenteral administration” of a pharmaceuticalcomposition includes any route of administration characterized byphysical breaching of a tissue of a subject and administration of thepharmaceutical composition through the breach in the tissue. Parenteraladministration thus includes, but is not limited to, administration of apharmaceutical composition by injection of the composition, byapplication of the composition through a surgical incision, byapplication of the composition through a tissue-penetrating non-surgicalwound, and the like. In particular, parenteral administration iscontemplated to include, but is not limited to, subcutaneous,intraperitoneal, intramuscular, intrasternal injection, and kidneydialytic infusion techniques.

Formulations of a pharmaceutical composition suitable for parenteraladministration comprise the active ingredient combined with apharmaceutically acceptable carrier, such as sterile water or sterileisotonic saline. Such formulations may be prepared, packaged, or sold ina form suitable for bolus administration or for continuousadministration. Injectable formulations may be prepared, packaged, orsold in unit dosage form, such as in ampules or in multi-dose containerscontaining a preservative. Formulations for parenteral administrationinclude, but are not limited to, suspensions, solutions, emulsions inoily or aqueous vehicles, pastes, and implantable sustained-release orbiodegradable formulations. Such formulations may further comprise oneor more additional ingredients including, but not limited to,suspending, stabilizing, or dispersing agents. In one embodiment of aformulation for parenteral administration, the active ingredient isprovided in dry (i.e., powder or granular) form for reconstitution witha suitable vehicle (e.g., sterile pyrogen-free water) prior toparenteral administration of the reconstituted composition.

The pharmaceutical compositions may be prepared, packaged, or sold inthe form of a sterile injectable aqueous or oily suspension or solution.This suspension or solution may be formulated according to the knownart, and may comprise, in addition to the active ingredient, additionalingredients such as the dispersing agents, wetting agents, or suspendingagents described herein. Such sterile injectable formulations may beprepared using a non-toxic parenterally-acceptable diluent or solvent,such as water or 1,3-butane diol, for example. Other acceptable diluentsand solvents include, but are not limited to, Ringer's solution,isotonic sodium chloride solution, and fixed oils such as syntheticmono- or di-glycerides. Other parentally-administrable formulationswhich are useful include those which comprise the active ingredient inmicrocrystalline form, in a liposomal preparation, or as a component ofa biodegradable polymer systems. Compositions for sustained release orimplantation may comprise pharmaceutically acceptable polymeric orhydrophobic materials such as an emulsion, an ion exchange resin, asparingly soluble polymer, or a sparingly soluble salt.

As used herein, “additional ingredients” include, but are not limitedto, one or more of the following: excipients; surface active agents;dispersing agents; inert diluents; granulating and disintegratingagents; binding agents; lubricating agents; sweetening agents; flavoringagents; coloring agents; preservatives; physiologically degradablecompositions such as gelatin; aqueous vehicles and solvents; oilyvehicles and solvents; suspending agents; dispersing or wetting agents;emulsifying agents, demulcents; buffers; salts; thickening agents;fillers; emulsifying agents; antioxidants; antibiotics; antifungalagents; stabilizing agents; and pharmaceutically acceptable polymeric orhydrophobic materials. Other “additional ingredients” which may beincluded in the pharmaceutical compositions of the invention are knownin the art and described, for example in Genaro, ed. (1985, Remington'sPharmaceutical Sciences, Mack Publishing Co., Easton, Pa.), which isincorporated herein by reference.

Typically, dosages of the compound of the invention which may beadministered to an animal, preferably a human, will vary depending uponany number of factors, including but not limited to, the type of animaland type of disease state being treated, the age of the animal and theroute of administration.

The compound can be administered to an animal as frequently as severaltimes daily, or it may be administered less frequently, such as once aday, once a week, once every two weeks, once a month, or even lessfrequently, such as once every several months or even once a year orless. The frequency of the dose will be readily apparent to the skilledartisan and will depend upon any number of factors, such as, but notlimited to, the type and severity of the disease being treated, the typeand age of the animal, and the like. Preferably, the compound is, butneed not be, administered as a bolus injection that provides lastingeffects for at least one day following injection. The bolus injectioncan be provided intraperitoneally.

The present invention encompasses various kits which comprise acompound, including a Listeria vaccine strain comprising an antigenfused to a truncated ActA protein, or a fragment thereof, an antigenfised to a truncated ActA protein, or a fragment thereof, an applicator,and an instructional material which describes use of the compound toperform the methods of the invention. Although model kits are describedbelow, the contents of other useful kits will be apparent to the skilledartisan in light of the present disclosure. Each of these kits iscontemplated within the present invention.

In one aspect, the invention includes a kit for eliciting an enhancedimmune response to an antigen. The kit is used in the same manner as themethods disclosed herein for the present invention. Briefly, the kit maybe used to administer an Listeria vaccine strain comprising an antigenfused to a truncated ActA protein. Additionally, the kit comprises anapplicator and an instructional material for the use of the kit. Theseinstructions simply embody the examples provided herein.

The kit further includes a pharmaceutically-acceptable carrier. Thecomposition is provided in an appropriate amount as set forth elsewhereherein. Further, the route of administration and the frequency ofadministration are as previously set forth elsewhere herein.

In another aspect, the invention includes a kit for eliciting anenhanced immune response to an antigen. The kit is used in the samemanner as the methods disclosed herein for the present invention.Briefly, the kit may be used to administer an an antigen fused to atruncated ActA protein. Additionally, the kit comprises an applicatorand an instructional material for the use of the kit. These instructionssimply embody the examples provided herein.

The kit further includes a pharmaceutically-acceptable carrier. Thecomposition is provided in an appropriate amount as set forth elsewhereherein. Further, the route of administration and the frequency ofadministration are as previously set forth elsewhere herein.

EXPERIMENTAL EXAMPLES

The invention is now described with reference to the following Examples.These Examples are provided for the purpose of illustration only and theinvention should in no way be construed as being limited to theseExamples, but rather should be construed to encompass any and allvariations which become evident as a result of the teaching providedherein. Sewell et al. (2004, Arch. Otolaryngol. Head Neck Surg., 130:92-97) is hereby incorporated by reference in its entirety herein.

Example 1 Tumor Cell Lines

TC-1 is a lung epithelial cell from C57BL/6 mice immortalized by HPV-16E6 and E7 and transformed by pVEJB expressing activated human c-HA-ras.C3 is a mouse embryo cell frp, C57BL/6 mice immortalized with thecomplete genome of HPV 16 and transformed with pEJ-ras. EL-4/E7 is thethymoma EL-4 retrovirally transduced with E7.

Example 2 Comparison of Efficacy of Lm-GG/E7, Lm-AZ/E7 and Vac-SigE7Lamp

TC-1 (1×10⁵) or C-3 (5×10⁵) tumor cells were implanted subcutaneously inmice and allowed to grow for 7 to 9 days by which time they werepalpable (about 5 mm in size). Mice were then immunized i.p. with one ofthree constructs, Vac-SigE7Lamp (10⁷ PFU), Lm-E7 (10⁶ CFU) or Lm-LLO-E7(10⁷ CFU). Animals received Lm-LLO-E7 and LM-E7 on days 7 and 14.Surviving mice were re-challenged with 105 TC-1 on day 43.

Example 3 Comparison of Efficacy of Vac-LLO-E7, Vac-E7 and Vac-SigE7Lamp

Four groups of 8 mice were implanted with 10⁵ cells of TC-1. After 7days the tumors were approximately 4 mm in size. One group of mice wasuntreated. Each of the other groups received 10⁷ PFU of either Vac-E7,Vac-LLO-E7 or Vac-Sig-E7-lamp 7. A booster dose was administered on day14.

Example 4 Comparison of Efficacy of Vac-LLO-E7 and Lm-LLO-E7 withVarious Other Vectors

TC-1 tumor cells (2×10⁵) were implanted s.c. on the left flank in 96C57BL/6 mice and allowed to grow for 7 days. The mice were divided intogroups of 8 mice and each group was treated with one of the followingvaccine: naive (no vaccine); Vac SigE7Lamp, 10⁷ PFU, i.p.; Vac-LLO-E7,10⁷ PFU, i.p.; or Lm-LLO-E7, 10⁷ PFU, i.p. The animals received abooster immunization one week later. Tumor growth was followed every twodays by caliper measurement and recorded as the average of the narrowestand longest surface length. Immune parameters were also determined.

Example 5 Construction of Lm-LLOPEST-E7

The LLO-PEST-E7 fragment can be constructed via SOEing PCR. In Step 1 ofthis method, PCR reaction 1 uses primer pair GG-36/GG-78 or GG-77/AZ-9with pGG-55 for the template. PCR reaction 2 uses LLO-PEST and E7products from the first reaction as templates and the primers GG-36 andAZ-9. (SEQ ID NO:8) GG-36: 5′-GCTAGCCCTCCTTTGATTAGTATATTC-3′, (SEQ IDNO:9) GG-77: 5′-GCGGATGAAATCGATAAGCATGGAGATACACCTACA-3′, (SEQ ID NO:10)GG-78: 3′-CGCCTACTTTAGCTATTCGTACCTCTATGTGGATGT-5′ (SEQ ID NO:11) AZ-9:3′-GAGTCTTTGGTATTGGGCCC-5′.

In step 2, the final SOEing PCR product of 0.7 Kb is ligated into the TAvector pCR2.1.

In step 3, the LLO-PEST-E7 is digested from the plasmid with the enzymeNheI for 2 hours followed by ethanol precipitation and the enzyme XmaIovernight. The prfA fragment from pGG-49 is digested with the enzymeSalI for 2 hours followed by ethanol precipitation and XmaI overnight.pDP-2028 is digested with SalI and XbaI for 2 hours followed by ethanolprecipitation and resuspension in Tris:EDTA (TE). The fragment can bestored overnight at 4° C.

In step 4, the 0.7 Kb LLO-PEST-E7, 1.0 Kb prfA and the 9.7 Kb plasmidare ligated. This plasmid is then used to transform XFL-7. Secretion ofa 15 Kb fragment can be verified via Western blot. Efficacy is verifiedagainst TC-1 tumors.

Alternatively, a chromosomal integrant can be generated by amplifyingthe LLO-PEST-E7 fragment using the primer AZ-B (5′-GCTCTAGATTATGGTTTCTGAG-3′; SEQ ID NO:12) to install a 3′ XbaI site and primer ZY-3(5′-GGGGTACCCT CCTTTGATTAGTATAT-3′; SEQ ID NO:13) to install a 5′ KpnIsite. pZY-37 and the LLO-PEST-E7 fragment are digested with KpnI andXbaI separately or in NEB buffer 2+ BSA overnight. The fragment isligated into pZY-37 and the following protocol for chromosomalintegration is followed. Secretion and efficacy are verified asdescribed above.

Example 6 Construction of Lm-actA-E7

L. monocytogenes strain XFL7 (a prfA negative L. monocytogenes 10403sprovided by Dr. Jeff Miller, University of California Los Angeles, LosAngeles, Calif.) was the organism used in the cloning studies of theconstruct Lm-actA-E7. Lm-actA-E7 is a recombinant strain of L.monocytogenes, comprising a plasmid that express the E7 protein fused toa truncated version of the actA protein.

Lm-actA-E7 was generated by introducing a plasmid vector pDD-1constructed by modifying pDP-2028 (Ikonomidis et al., 1994, J. Exp. Med.180:2209-2218) into L. monocytogenes. The pDD-1 plasmid comprises anexpression cassette expressing a copy of the 310 bp hly promoter and thehly signal sequence (ss), (this gene drives the expression and secretionof the actA-E7 gene product), 1170 bp of the actA gene that comprisesfour PEST sequences (SEQ ID NO:24) (the truncated ActA polypeptideconsists of the first 390 amino acids of the molecule, SEQ ID NO:23), acopy of the 300 bp E7 gene (HPV tumor protein), a copy of the 1019 bpprfA gene (controls expression of the virulence genes) and a copy of theCAT gene (chloramphenicol resistance gene) for selection of transformedbacteria clones. (FIG. 7).

The hly promoter (pHly) and gene fragment were PCR amplified from pGG55(pLLO-E7, Gunn et al., 2001, J. Immunol. 167:6471-6479) using primer5′-GGGGTCTAGACCTCCTTTGATTAGTATATTC-3′ (Xba I site is underlined) (SEQ IDNO:14) and primer 5′-ATCTTCGCTATCTGTCGCCGCGGCGCGTGCTTCAGTTTGTTGCGC-′3(Not I site is underlined. The first 18 nucleotides are the ActA geneoverlap). (SEQ (SEQ ID NO:15). The actA gene was PCR amplified from theListeria monocytogenes 10403s wildtype genome using primer 5′-GCGCAACAAACTGAAGCAGCGGCCGCGGCGACAGATAGCGAAGAT-3′ (SEQ ID NO:16) and primer5′-TGTAGGTGTATCTCCATGCTCGAGAGCTAGGCGATCAATTTC-3′ (SEQ ID NO:17). The E7gene was PCR amplified from pGG55 (pLLO-E7) using primer5′-GGAATTGATCGCCTAGCTCTCGAGCATGGAGATACACCTACA-3′ (SEQ ID NO:18) andprimer 5′-AAACGGATTTATTTAGATCCCGGGTTATG GTTTCTGAGAACA-3′ (SEQ ID NO:19).The prfA gene was PCR amplified from the Listeria monocytogenes 10403swildtype genome using primer 5′-TGTTCTCAGAAACCATAACCCGGGATCTAAATAAATCCGTTT-3′ (SEQ ID NO:20) and primer5′-GGGGGTCGACCAGCTCTTCTTGGTGAAG-3′ (SEQ ID NO:21). The hly promoter wasfused to the actA gene (pHly-actA) was PCR generated and amplified frompurified pHly DNA and purified actA DNA using the pHly primer (upstream)5′-GGGGTCTAGACCTCCTTTGATTAGTATATTC-3′ (SEQ ID NO:14) and acta primer(downstream) 5′-TGTAGGTGTATCTCCATGCTCGAGAGCTAGGCGATCAATTTC-3′ (SEQ IDNO:17).

The E7 gene fused to the prfA gene (E7-prfA) was PCR generated andamplified from purified E7 DNA and purified prfA DNA using the E7 primer(upstream) GGAATTGATCGCCTAGCTCTCGAGCATGGAGATACACCTACA-3′ (SEQ ID NO:18)and prfA gene primer (downstream) 5′-GGGGGTCGACCAGCTCTTCTTG GTGAAG-3′(SEQ ID NO:21).

The pHly-actA fusion product fused to the E7-prfA fusion product is PCRgenerated and amplified from purified fused pHly-actA DNA product andpurified fused E7-prfA DNA product using the pHly primer (upstream)5′-GGGGTCTAGACCTCCTT TGATTAGTATATTC-3′ (SEQ ID NO:14) and prfA geneprimer (downstream) 5′-GGGGGTCGACCAGCTCTTCTTGGTGAAG-3′ (SEQ ID NO:21)and ligated into pCRII (Invitrogen, La Jolla, Calif.). Competent E. coli(TOP10′F, Invitrogen, La Jolla, Calif.) were transformed withpCRII-ActAE7. After lysis and isolation, the plasmid was screened byrestriction analysis using BamHI (expected fragment sizes 770 bp and6400 bp (or when the insert was reversed into the vector: 2500 bp and4100 bp)) and BstXI (expected fragment sizes 2800 bp and 3900 bp) andalso screened with PCR analysis using the pHly primer (upstream)5′-GGGGTCTAGACCTCCTTTGATTAGTATATTC-3′ (SEQ ID NO:14) and the prfA geneprimer (downstream) 5′-GGGGGTCGACCAGC TCTTCTTGGTGAAG-3′ (SEQ ID NO:21).

The pHly-ActA-E7-PrfA DNA insert was excised from pCRII by doubledigestion with Xba I and Sal I and ligated into pDP-2028 also digestedwith Xba I and Sal I. After transforming TOP10′F competent E. coli(Invitrogen, La Jolla, Calif.) with expression system pActAE7,chloramphenicol resistant clones were screened by PCR analysis using thepHly primer (upstream) 5′-GGGGTCTAGACCTCCTTTGATT AGTATATTC-3′ (SEQ IDNO:14) and the prfa gene primer (downstream)5′-GGGGGTCGACCAGCTCTTCTTGGTGAAG-3′ (SEQ ID NO:21). A clone comprisingpActAE7 was grown in brain heart infusion medium (with chloramphenicol(20 μg/ml), Difco, Detroit, Mich.) and pActAE7 was isolated from thebacteria cell using a midiprep DNA purification system kit (Promega,Madison, Wis.). A prfA-negative strain of penicillin-treated Listeria(strain XFL-7) was transformed with expression system pActAE7, asdescribed in Ikonomidis et al. (1994, J. Exp. Med. 180: 2209-2218) andclones were selected for the retention of the plasmid in vivo. Cloneswere grown in brain heart infusion with chloramphenicol (20 μg/ml) at37° C. Bacteria were frozen in aliquots at −80° C.

Example 7 Immunoblot Verification of Antigen Expression

In order to verify that Lm-ActA-E7 secretes a fusion protein of thecorrect molecular weight (about 64 kD), recombinant bacteria were grownovernight at 37° C. in Luria-Bertoni broth and pelleted. About 18milliliters of supernatant from each culture was TCA precipitated and E7expression was analyzed by Western blot. Specifically, clones .001′2.5.3and 2.5.4 were grown in Luria-Bertoni medium (Difco, Detroit, Mich.) at37° C. Supernatants were TCA precipitated and resuspended in 1× samplebuffer with 0.1N NaOH. Identical amounts of each TCA precipitatedsupernatant were loaded on 4-20% Tris-glycine SDS-PAGE gel (NOVEX, SanDiego, Calif.). The gel was transferred to polyvinylidene difluoridemembrane and probed with anti-E7 mAb at a dilution of 1:2500 (ZymedLaboratories, South San Francisco, Calif.). The secondary Ab wasHRP-conjugated anti-mouse IgG, diluted 1:5000 (Amersham PharmaciaBiotech, Little Chalfont, U.K.). Blots were developed with Amersham ECLdetection reagents and exposed to Hyperfilm (Amersham Pharmacia Biotech)(FIG. 8).

Example 8 Anti-Tumor Immunity of Lm-ActA-E7

To compare the anti-tumor immunity induced by Lm-ActA-E7 versusLm-LLO-E7 and Lm-E7, 2×10⁵ TC-1 tumor cells were implantedsubcutaneously in mice and allowed to grow for 7 days by which time theywere palpable (approximately 5 millimeters in size). Mice were thenimmunized intraperitoneally with one LD₅₀ of either Lm-ActA-E7 (5×10⁸CFU), Lm-LLO-E7 (10⁸ CFU) or Lm-E7 (10⁶ CFU) on days 7 and 14 followingTC-1 cell implantation. Tumor growth was measured periodically withcalipers. By day 26 all of the animals in the Lm-LLO-E7 and Lm-ActA-E7were tumor free and remained so whereas all of the naïve animals and theanimals that were immunized with Lm-E7 grew large tumors (FIG. 9).

Example 9 Ability of Lm-ActA-E7 to Enhance E7 Specific Immunity

To analyze the ability of Lm-ActA-E7 to enhance antigen specificimmunity, 500 μl of MATRIGEL™, comprising 100 μl of 2×10⁵ TC-1 tumorcells in phosphate buffered saline plus 400 μl of MATRIGEL™ (BDBiosciences, Franklin Lakes, N.J.) were implanted subcutaneously on theleft flank of 12 C57BL/6 mice. The mice were divided into 4 groups, 3mice per group. On day 7, 14 and 21 each group of mice was administered(intraperitoneally) either naive (untreated), Lm-LLO-E7 (1×10⁷ CFU),Lm-E7 (1×10⁶ CFU), or Lm ActA E7 (2×10⁸ CFU). Spleens and tumors wereharvested 7 days following the last immunization on day 21. TumorMATRIGELs were removed from the mice and placed in tubes containing 2milliliters of RP 10 medium on ice and incubated at 4° C. overnight. Thetumors were then minced with forceps, cut into 2 millimeter blocks andtreated with 3 ml of enzyme mixture (0.2 mg/ml collagenase-P, 1 mg/mlDNAse-1 in PBS) and incubated at 37° C. for 1 hour. The tissuesuspension was then filtered through nylon mesh, washed with 5% fetalbovine serum+0.05% of NaN₃ in PBS for tetramer and IFN-gamma staining.

Splenocytes and tumor cells were incubated with 1 μm E7 peptide for 5hours in the presence of the Golgi transport inhibitor brefeldin A at adensity of 10⁷ cells/ml. Cells were washed twice and incubated in 50 μlof anti-mouse Fc receptor supernatant (2.4 G2) for 1 hour or overnightat 4° C. Cells were stained for surface molecules CD8 and CD62L,permeabilized, fixed using the permeabilization kit Golgi-stop orGolgi-Plug (Pharmingen, San Diego, Calif.) and then stained forIFN-gamma. Typically, 500,000 events were acquired using two-laser flowcytometer FACS Calibur and analyzed using Cellquest Software (BectonDickinson, Franklin Lakes, N.J.). The percentage of IFN-gamma secretingcells within the activated (CD62L low) CD8⁺ T cells was calculated. CD8⁺T cells secreting IFN-gamma infiltrate the tumors of mice administeredLm-LLO-E7 and Lm-ActA-E7 to a much greater degree than in miceadministered Lm-E7 or naive mice (FIG. 10).

For tetramer staining, H-2D^(b) tetramer was loaded with phycoerythrin(PE) conjugated E7 peptide (RAHYNIVTF, SEQ ID NO:22) and stained at roomtemperature for 1 hour and then stained with anti-allophycocyanin (APC)conjugated MEL-14 (CD62L) and FITC-conjugated CD8β on ice for 30 min.Cells were analyzed comparing tetramer+CD8⁺ CD62L^(low) cells generatedby the different recombinant Listeria in the spleen and in the tumor.Lm-ActA-E7 immunized mice produce a greater number of tumor-infiltratingE7 tetramer specific CD8⁺ cells than mice administered Lm-LLO-E7, and afar greater number of tumor-infiltrating E7 tetramer specific CD8⁺ cellsthan mice administered Lm-E7 and naive mice (FIG. 11).

The data disclosed herein demonstrate a distinct correlation between thenumbers of CD8⁺ T cells infiltrating the tumors and the ability of theconstructs to kill the tumor. Thus, Lm-LLO-E7 and Lm-ActA-E7 are equallyeffective at inducing the regression of TC-1 and also induce the largestnumber of infiltrating CD8⁺ T cells measured as E7 specific IFN-gammasecreting cells or as E7 specific tetramer positive cells.

The disclosures of each and every patent, patent application, andpublication cited herein are hereby incorporated by reference in theirentirety.

While this invention has been disclosed with reference to specificembodiments, it is apparent that other embodiments and variations ofthis invention may be devised by others skilled in the art withoutdeparting from the true spirit and scope of the invention. The appendedclaims are intended to be construed to include all such embodiments andequivalent variations.

1. A method for enhancing the immunogenicity of an antigen comprisingfusing to the antigen a truncated ActA protein, or a fragment thereof.2. The method of claim 1, wherein the truncated ActA protein is at least95% homologous to the sequence set forth in SEQ ID NO:23.
 3. The methodof claim 1, wherein the truncated ActA protein, or fragment thereof,comprises the sequence set forth in SEQ ID NO:23.
 4. The method of claim1, wherein the truncated ActA protein consists of the sequence set forthin SEQ ID NO:23.
 5. A vector comprising an isolated nucleic acidencoding a truncated ActA protein, or a fragment thereof, and anisolated nucleic acid encoding an antigen, wherein the isolated nucleicacid encoding a truncated ActA protein has 95% identity to the nucleicacid sequence set forth in SEQ ID NO:24, and further wherein when theisolated nucleic acid encoding a truncated ActA and the isolated nucleicacid encoding an antigen are expressed in a cell, the isolated nucleicacid encoding a truncated ActA and the isolated nucleic acid encoding anantigen are expressed as a fusion protein.
 6. The vector of claim 5,wherein the isolated nucleic acid encoding a truncated ActA protein, orfragment thereof, comprises the sequence set forth in SEQ ID NO:24. 7.The vector of claim 5, wherein the isolated nucleic acid encoding atruncated ActA protein, or fragment thereof, consists of the sequenceset forth in SEQ ID NO:24.
 8. A Listeria vaccine strain comprising anantigen fused to a truncated ActA protein, or fragment thereof.
 9. TheListeria vaccine strain of claim 8, wherein the truncated ActA proteinis at least 95% homologous to the sequence set forth in SEQ ID NO:23.10. The Listeria vaccine strain of claim 8, wherein the truncated ActAprotein, or fragment thereof, comprises the sequence set forth in SEQ IDNO:23.
 11. The Listeria vaccine strain of claim 8, wherein the truncatedActA protein consists of the sequence set forth in SEQ ID NO:23.
 12. TheListeria vaccine strain of claim 8, wherein the antigen and thetruncated ActA protein, or fragment thereof, are encoded by a vector.13. The Listeria vaccine strain of claim 8, where the Listeria vaccinestrain is the species Listeria monocytogenes.
 14. A method of elicitingan enhanced immune response to an antigen, the method comprisingadministering to a mammal an effective amount of a compositioncomprising a Listeria vaccine strain, wherein the Listeria vaccinestrain comprises an antigen fused to a truncated ActA protein, or afragment thereof.
 15. The method of claim 14, wherein the mammal is ahuman.
 16. The method of claim 14, wherein the truncated ActA protein isat least 95% homologous to the sequence set forth in SEQ ID NO:23. 17.The method of claim 14, wherein the truncated ActA protein, or fragmentthereof, comprises the sequence set forth in SEQ ID NO:23.
 18. Themethod of claim 14, wherein the truncated ActA protein consists of thesequence set forth in SEQ ID NO:23.
 19. The method of claim 14, whereinthe composition is suspended in a pharmaceutically acceptable carrier.20. A kit for eliciting an enhanced immune response to an antigen, thekit comprising a Listeria vaccine strain, wherein the Listeria vaccinestrain comprises an antigen fused to a truncated ActA protein, orfragment thereof, and a pharmaceutically acceptable carrier, said kitfurther comprising an applicator, and an instructional material for usethereof.
 21. A kit for eliciting an enhanced immune response to anantigen, the kit comprising an antigen fused to a truncated ActAprotein, or fragment thereof, and a pharmaceutically acceptable carrier,said kit further comprising an applicator, and an instructional materialfor use thereof.
 22. An isolated nucleic acid encoding a truncated ActAprotein, or a fragment thereof, and an antigen, wherein said isolatednucleic acid encoding the truncated ActA protein has 95% identity to thenucleic acid sequence set forth in SEQ ID NO:24.
 23. The isolatednucleic acid of claim 22, wherein the truncated ActA protein, orfragment thereof, comprises the sequence set forth in SEQ ID NO:24. 24.The isolated nucleic acid of claim 22, wherein the truncated ActAprotein consists of the sequence set forth in SEQ ID NO:24.
 25. Anisolated fusion protein comprising a truncated ActA protein, or afragment thereof, and an antigen, wherein said isolated fusion proteincomprises a truncated ActA protein having 95% identity to the amino acidsequence set forth in SEQ ID NO:23.
 26. The fusion protein of claim 25,wherein the truncated ActA protein, or fragment thereof, comprises thesequence set forth in SEQ ID NO:23.
 27. The fusion protein of claim 25,wherein the truncated ActA protein consists of the sequence set forth inSEQ ID NO:23.
 28. The fusion protein of claim 25, wherein the fusionprotein is suspended in a pharmaceutically acceptable carrier.
 29. Thefusion protein of claim 26, wherein the fusion protein is suspended in apharmaceutically acceptable carrier.
 30. The fusion protein of claim 27,wherein the fusion protein is suspended in a pharmaceutically acceptablecarrier.